SMOKERS & SMOKEHOUSES

Meat smokers and smokehouses are used to smoke products like meat, sausages, poultry or fish. The properly designed meat smoker must:

Generate smoke (cold and hot).

Be able to achieve and maintain desired temperatures inside.

Be able to cook the product to the required inside meat temperature, most often 152° - 160° F (67°-72° C).

This last cooking requirement can be performed outside of a smoker by poaching meat in hot water or baking it in the oven. The sophistication of the device is unimportant; smoke can be created in both a 55-gallon drum smoker and a home made box. Some meats are cooked in a smoker to make them ready to eat, while some will only receive a smoky flavor and will be taken out for prolonged periods of air-drying.

The design of a smoker remains relatively easy unless cooking meats or sausages to the ready to eat temperature is a requirement. But why cook a sausage in a smoker? This task can be accomplished much faster and more easily by heating the sausage in water. Baking in an oven is also an option as long as the temperature can be kept as low as 170° F (76° C). Heating sausages in water is not a trick or shortcut, but an acceptable and even proper way of preparing sausages for centuries. Boiled ham can be found in every supermarket. If we boil the best hams in the world, then why not sausage? Well, we do, some of the best sausages from Europe are first smoked in a smoker, and then finished by poaching them in water at about 176° F (80° C).

Keep in mind that we don’t use the word “boil” when heating meat inside a pot full of water. We use “heat” to stress the fact that the water must be kept at 158°-176° F (70°-90° C), and not at its boiling point, which is 212° F (100° C). You could bring home smoked meats (not cooked yet) and place them directly in a freezer. Then later, when needed, they can be thawed and poached in water. When smoking meats with a separate fire pit/smoke generator, we have more time to enjoy ourselves because we don’t have to check the temperature so often. If the plan is to eat the meat within a matter of days, it doesn’t make much of a difference whether we smoke with cold, warm, or hot smoke.

However, we are playing a completely different game if we use the smoker to smoke and cook the meat. Now outside temperatures become important factors. The smoker may need some insulation to maintain appropriate temperatures, especially during the colder months. Holding internal temperatures of 152° – 160° F (67°-72° C) can be difficult in cold climates when the smoker is situated outside. Maintaining temperatures by burning wood in a 55 gallon metal drum is a hit or miss proposition. The best solution, which is incidentally used in commercial smokers, is to rely less on the smoke generator or fire pit as our only heating source, but to install a second independent heat source.

The heating process is now shared by two separate components:

a fire pit to generate smoke.

an electrical heating element or gas burner to generate heat.

By using two components we can produce a quality product in any climate. A metal drum, unless insulated, is still a poor choice in hard winters, but anything built with brick or thick wood is fine.

It should be noted that the whole design changes drastically when there is a supply of electricity. With a stand-alone fire pit, we can use a barbecue starter wire for heating wood chips or sawdust until they start producing smoke. Inside the smoker we can place an electric heating element to supply heat with a turn of the dial. By adding a thermostat to the arrangement, we can preset the temperature of a smoker. A gas burner can also be used as a source of heat.

Every smoker, no matter how simple or sophisticated, consists of the following parts:

a source of smoke (fire pit).

a smoking chamber, any device or enclosure that will confine smoke inside.

sticks, hooks or screens (hardware used to hang the meat in the smoking chamber).

draft controls (dampers).

The most important parts are the smoke generator (fire pit) and smoke chamber. They could be part of the same unit or they could stand separately. For example, a drum smoker can be placed over a fire pit or it can be placed on a lower level connected by a metal pipe with a separate fire pit to aid smoke flow.

Smoker with a fire pit inside (one unit smoker)

Wood fired smoker

Using firewood to slowly bring the temperature to 170° F (76° C) and maintain it at that level for about 30 minutes is extremely difficult. Irregular sizes of wood need to be constantly added on. One moment of negligence and the temperature soars over 200° F. Without a safety baffle, this can be disastrous for a smoker. All the fat inside the sausage will melt, leak through the casings, and drop on the small flames in the fire pit below. These little flames will not be little anymore. If left unattended, a small controlled flame will turn into a raging fire. The sausage casings will become so dry and brittle that the sausages themselves will fall down into the fire pit.

Note when we use wood to burn an open fire we assume that the flames are not very long. The reason they are short is that they are cooled by the air above. Once the temperature in a closed firebox goes up the flames will also become longer providing there is a supply of fresh air. For example in a well designed masonry heater the temperature can reach 1800° F (1000° C) and the flames may reach 5' in length.

Flame and heat protection is a big problem for small smokers since the distance between the fire pit and the hanging meats is so short. That is why smaller smokers must have a safety feature called a “baffle” built into it to prevent this kind of scenario. Most often a baffle is some type of a perforated metal plate that physically separates the fire pit from the smoking chamber. One of the best baffles is river gravel placed on any suitable screen.

In the first drawing shows a very functional although not a typical baffle. This stainless steel enclosure with hundreds of holes creates a formidable safety screen for any possible flames from below. The smoker has also a separate fire pit that is connected by a 6" steel pipe. Its outlet is visible under gas burner that is used for cooking only.

Smaller factory made smokers also employ smoke generating unit inside and some protection is needed like a baffle or a flame/heat shield.

Sausage Maker 100 lb - electric

Sausage Maker 100 lb - gas

Smokers with a separate smoke generator

There is a small smoker made by Bradley Technologies with a separate smoke generator that employs an original way of producing smoke. Prefabricated blocks of wood (flavor bisquettes) are fed vertically into the smoke generator unit and one by one burn there generating smoke. The smoke generator has a short pipe that fits into the smoking chamber. A nice unit but there is a catch....you are dependent on the company or its distributors to deliver bisquettes which come in different flavors (hickory, apple, alder and others).

Bradley Technologies smoker

Bradley smoke generator

To prevent flames and fully utilize the little space small smokers have at their disposal, a separate smoke generator should be used. The smoker should stand on some sort of base, either a pipe or dug out soil trench, and enter the bottom of the smoker. The popular 55-gallon metal drum looks especially nice when standing on a round base.

The benefits of of a separate smoke generator are numerous:

ability to provide cooler smoke

better flames and heat control

easier control of a smoking/cooking process

Using free standing smoke generator/fire pit we don't have to worry about flames. Don't let looks of those barrels fool you-those smokers are capable of producing the highest quality products. They can be simple common drums or expensive masonry types with all kinds of bells and whistles. The design of a great smoker has remained the same for centuries - two separate parts: smoker and a fire pit/smoke generator.

In industrial smokehouses steam, water spraying, and other microprocessor controlled functions take care of the entire smoking and cooking operations.The smoke generator is a separate unit standing outside of the smoker and is connected to it with a pipe. Electric blowers blow the smoke inside of the unit. Any small heat fluctuation coming from the smoke generator will not have much effect on the temperature inside the smoking chamber. This gives us more freedom because there is no need to open the smoker’s door (or top cover) to check the smoke flow.

Different methods are used to generate smoke in commercial smokehouses. A widely used technique is to pyrolyze hardwood chips or sawdust. Wood pieces are fed into a gas or electrically heated metal surface at 662° –752° F (350°-400° C).

With other methods, a block of wood is pushed against rotating a metal wheel and temperatures become high enough for the wood to start smoking. Electrical blowers push the smoke into ducts leading into the smokehouse.

Reich smokehouse

Smokehouse Burners

Smokehouse heating systems depend on the type of fuel chosen. If heating is to be efficient and easy to control, the smokehouse must be well insulated, what becomes especially important in cold weather.

There are three types of fuel used in smokers

Wood - commonly used in home made smokers situated outside.

Electricity - factory made smokers. Wood chips or sawdust are still needed for smoke generation.

Gas - natural or propane. Preferred fuel in large industrial smokers. Wood chips or sawdust are still needed for smoke generation.

Wood is the traditionally used fuel in outside smokehouses because:

It is easy to obtain

It is free

It is dependable

It is fun - when burning wood in a simple home made smoker, it looks prettier than any factory made mode

Wood presents very few safety problems. There is a remote chance of a fire and no chance of explosion which may occur in a gas fired systems. To control and maintain the temperature when burning wood is difficult, especially when using a smaller smokehouse. Here, the fire pit design will be a key to the success and great location with air controlling dampers will play a crucial role. Some smokers use charcoal as fuel though wood chips or sawdust is still needed to produce smoke. Charcoal briquettes may be an acceptable fuel for a barbecue but don’t belong in a real smoking category as they often leave an unpleasant under taste in smoked products. If as the last resort you have to use them, make sure they burn outside of a smoker first until thoroughly covered with white ash before entering the smoking chamber.

Fire Pit

A fire pit or fire box is the area of the smoker where we burn wood to produce smoke or to generate heat to cook meat products. It can be an integral part of the smoker or free standing separate unit connected to a smoker by a pipe or dug out trench in the ground. It could be a smaller barrel or a metal box. It may be made of reinforced concrete or from firebricks. The combustion efficiency inside the fire box depends on the ways fresh air is supplied into the burning wood. All smokers employ a very simple system of draft control as the the main purpose of smoking is to create smoke at low temperatures and that can be often accomplished without any draft system.

If we want to control the burning process by using fresh air dampers, how we place wood controls the rate of burning and temperatures in a fire box. A baffle can be placed vertically and it will direct heat in a different direction now. The less clearance between the top of the baffle, the more heat will be supplied to the top of the fire box.

Note warm air or smoke will always go up.

Simple firebox

Fire box with a vertical baffle

The three classical ways of placing wood in a fire box follow below:

Directly on the ground, known as the hearth bottom-grate

Above the ground on a grate, known as a stool-grate

Above the ground on a grate, known as a raised stool-grate

Hearth Bottom Grate

The drawing below shows the most common way of positioning wood when smoking. When wood is placed directly on the ground the whole air enters from above. This is the way fireplaces work and though all air seems to bypass the wood, enough of it reacts with fire to maintain combustion. It is obvious from the drawing that a strong draft has very little influence on a combustion process as the air will only stream faster over the fire.

The rate of combustion and temperature is controlled by the amount of wood placed in a fire pit and as the air is consumed, a new fresh air comes into its place. The rate of combustion is independent of the draft and the fire burns as if no chimney existed. To be able to control burning, the air opening has to be greatly decreased and a damper will start exercising control. Wood burns from front to back. When placing wood on the ground in a firebox with fresh air flowing in freely, the higher temperature will be in the back of a firebox or the barrel.

Stool Grate

The drawing below is an example of a closed fire box used in a heating stove. The entering air below the wood has a greater density than the hot air above the wood, this creates a difference of pressure (draft) and the only possible way is to go up through the wood. The burning coals will deprive the streaming air of its oxygen and that sets the temperature as no more fresh air is available.

Placing wood on a grate permits the introduction of primary air below the burning wood and better combustion. Here the coal bed physically separates fresh air below from the warm air above, a natural draft is created and all air has to flow through burning coals or wood. This is the most effective solution permitting a great deal of control.

Raised Stool Grate

The drawing below depicts a smaller amount of air flowing through the burning wood and the larger portion blows over the wood increasing the rate of burning. In this case the rate of combustion can be easily controlled by adjusting the air supply under the fire.

Summary on fire box types

The rate of combustion is easiest to control in the stool-grate design and most difficult in the hearth bottom-grate type. Smoking can be easily done with an open fire (hearth-bottom grate) and adding more sawdust to kindling fire allows for some control at least in respect to smoke. The raised stool grate type can be an effective tool for switching over from smoking to the cooking process. When smoking, the bottom damper has to be shut tight and the top damper open. The firebox becomes the hearth bottom-grate type and by adjusting the top damper we can choke down the air supply and the wood will start smoking. Needless to say we still need to add sawdust or wood chips into the hot coals.

To control combustion and temperatures when cooking, a bottom damper can be adjusted to provide more air which will increase the burning rate and will create more heat and higher temperatures. By the same token the amount of smoke created will be decreasing. A correctly designed stool-grate fire pit will allow to switch from smoking to cooking by opening the fresh air damper located below the grate level.

The way most smokers operate is to have an unrestricted flow of the incoming air into the flue (pipe) and the smoke is rushing from the fire pit into the smoking chamber with some unburned particles. The temperature is set by the rate of burning wood and the excess fresh air is rushing into the pipe together with the smoke. This is a welcome scenario as this fresh air brings moisture with it into the smoker preventing the drying out of sausage casings.

Note in order for the dampers to perform their designated function, the fire box and its door must be made tight. If proper rules for efficient combustion are observed the wood becomes a very clean fuel.

The grate significantly increases the efficiency of combustion. The firebox design is further enhanced by sloping the floor of the firebox from the sidewalls down to the grate.

Secondary combustion

Secondary combustion means adding pre-heated fresh air above the burning wood which will add fresh oxygen into the flames and the temperature will rise allowing cleaner and more efficient combustion. There will be less soot and other unburned particles and less smoke as well. This is not needed during the smoking process but may be of use when we start cooking meats.

It is achieved by placing a baffle in the rear of the fire pit to prevent smoke from rushing directly into the flue and to re-direct it into the area where a secondary air is entering the chamber. In old times the blacksmith was manually pumping more air into the fire to create high temperatures that made metals softer and pliable and that was excactly secondary combustion even though the air he supplied was not pre-heated. Incoming air is preheated in a confined but hot area before being divided into two separate streams: the primary (lower) and the secondary (higher). The smoke cannot go straight up the flue anymore and has to return to sneak through the only available opening where it picks up fresh and hot secondary air and burns cleaner now due to much higher temperatures.

Note: bluish flames indicate complete combustion

The air for secondary combustion is delivered in a higher part of the fire box, just before smoke enters the flue. The idea behind secondary combustion is to recover some of the heat that will otherwise go up the chimney by more efficient and cleaner burning of the wood. Secondary combustion can be employed in any of the fire pit arrangements as long as there is a baffle and secondary air coming close to the flue as shown in the following drawing.

The efficiency will further improve if the secondary air in C is preheated.

Preheating secondary air

In the above drawing the pipe travels through the flame area and the air inside gets heated and escapes through a series of holes drilled in the end section of the pipe. The simplest secondary air delivery system is just a covered hole located near the upper part of the baffle. The hole can be drilled in the required area and the pipe can be directly inserted into the hole. It can be welded or threaded and secured with nuts.

The above drawing depicts a very clever solution where the baffle acts as a pre-heat air delivery vehicle. Depending whether a grate is employed a pipe can be connected to the baffle on the bottom of a fire box or can run over the grate. Baffle plates should be made of a thicker material.

Grate made of metal pipe 1/2”-1” diameter. Small holes 1/8” diameter supplying secondary hot air.

Fire pit placement in smokers

If a fire pit will occupy the bottom part of a barrel some steps must be taken to slow down the flow of the smoke and evenly distribute it inside of the chamber. This requires the installation of one or two baffle plates. The heat conduction will also be slowed down and the whole smoking and cooking process will be easier to control. The unit will have higher efficiency and less wood will be consumed. A fire pit can be a 2 - 3 ft deep hole in the ground, it can be round, square, rectangular, whatever, but it has to be covered with a sheet of metal. The hole should be 18 – 24” wide, the bigger diameter the more wood can be burned inside and more heat will be produced, which may be needed when cooking at low outside temperatures. The deeper the hole the better the draft will be. Anything deeper than 3 ft will make it impractical to clean up the ashes.

A metal barrel of smaller size can be used for a fire pit or a large 55 gal (200 l) barrel can be cut in half and embedded in the ground. A metal box of suitable dimensions can also be used. Using concrete blocks or masonry bricks will only make a temporary arrangement as they will start cracking. Firebricks and refractory fire clay is an acceptable and commonly used solution.

Adding Heating

The wood fired traditional smoker is a beautiful design capable of producing the highest quality product, but a smoker can become more user friendly by using additional types of fuel, like electricity or gas. Smoke will still be generated by burning wood chips in a preferably free standing smoke generator (fire pit), but the smoking chamber, which now becomes a cooking chamber, will benefit greatly with the addition of a controllable heating element or a gas burner.

This will give us the following advantages:

Heat on demand - just with the turn of a dial

Very accurate temperature control - a thermostat can be added to a heating element and we can go and watch TV

Total portability of a propane gas tank and burner

Ability to easily use propane fuel - a great aid for those smoking outside city limits without electricity

Consistent physical size and dimension of the smoker, all that is needed is installing a heating element or gas burner inside of a fire box.

On demand source of additional heat - a smoker can fully operate in its wood burning mode and the electric or gas option could be applied in very cold weather.

Electricity

Depending on location, can be inexpensive or very costly and can be a cost factor when smoking a product for two days or longer. Its advantages are that it is easy to use and allows for a precise temperature control especially when the smoker has a thermostat. An extension cable can provide electricity to the outside located smokehouse but a permanent electrical connection will be more elegant. A conduit pipe can be run underground to the point where a junction box could be installed. Small 500 W or 1000 W heating elements will use 115 volts but anything bigger than 2000 W will need 220 volts. Electrical heating is a popular method for smokers of smaller size.

With electricity there are are no safety concerns. In the worst case we may blow a fuse which is not a great deal.

From a technical point of view installing electrical burners is much easier than putting together a gas system as we don't have to deal with safety issues like flame blow out. There is no need for thermocouples and safety valves and the installation costs are much lower. Much less of a technical know-how is needed to put a system together. If a smokehouse is the size of a refrigerator you will need a stronger electrical burner (5000 W). Another burner can be easily added, too. Besides burners, many other devices (thermostat, control lamps, outside lamps, blower, smoke generator etc.).

Many factory made smokehouses can be ordered to run on either electricity or gas.

Gas is the cheapest energy and that is why it is used in commercial smokers and other kitchen equipment. Gas burners are easy to control and are able to supply huge amounts of heat. On a downside they present a few safety problems.

There are basically two types of gas:

Natural gas - no colour or smell, consisting mainly of methane (80 – 95%) and other gases like carbon dioxide, carbon monoxide, nitrogen, helium and argon. Its characteristic and unpleasant odour is achieved by purposely adding chemicals that create that smell. The natural gas pressure is very low and it varies from 6 to 10 of WC (water column). This is less than 1 PSI.

To use natural gas a gas pipe, commonly ½” diameter, has to be brought into the smoker and terminated with a valve. On the other side of the valve there will be a fitting and supply line to the burner. Large metropolitan areas are normally piped for natural gas but in some states, for example Florida, the natural gas is not available in most parts of the state. The disadvantage of a natural gas connection is that it requires metal pipe lines which once in place, can not be moved with a smokehouse to a new location. The amount of gas that can be delivered to the smokehouse depends on the pressure in the local system, length of pipe run, pipe size, the number of turns and the meter capacity. The disadvantage of a gas installation is its very permanent installation, metal pipe lines and more technical expertise needed for making connections. Its main plus is that you never run out of gas.

Propane – made by distilling a natural gas. Propane is heavier than a natural gas or air and it is stored in tanks as a liquid, under pressure. At 0° F the tank pressure is 24 PSI, at 30° F the pressure is at 51 PSI, at 70° F the pressure is 100 PSI, at 90° F it is 150 PSI and at 130° it is 260 PSI. When a propane tank reaches 120° F, the pressure inside is trippled and the tank may release some of the excess pressure through the safety relief valve. There are many camping units with one or two burners and different size propane bottles available at all major department stores. A typical grill's 20-pound cylinder holds five gallons of propane. The propane is filled in the bottle as a liquid, and the new valves have a float that rises as the bottle is filled to lock off the opening once the tank has reached 80 percent full.

Gas Burners

Both natural gas and propane burners work on the same principle called the "venturi effect". It says that as a gas or fluid passes through a pipe that narrows or widens, the velocity and pressure of the gas or fluid vary. As the pipe narrows, the gas flows more rapidly. What sounds like a surprise but holds true, is that when the fluid or gas flows faster through the narrow sections, the pressure actually decreases rather than increases. The venturi tube is a large diameter tube, gradually feeding into a smaller tube and then gradually becoming a larger tube.

The most important part of the burner is the orifice plug with the hole in it. This is the point where the gas escapes from the hose or a pipe and enters the mixing bell of the burner. Orifice plugs are replaceable and screwed into the orifice spud. Nearly all atmospheric (venturi) burners have a gas orifice that is accurately fixed in the burner throat providing air intake. The hole in the orifice is very small to provide the correct gas flow and to provide sufficient velocity to ensure there is a suction (vacuum) available for the correct air inspiration.

There are orifice charts that specify what diameter orifice hole should be drilled for particular burner. Those holes are normally very small, about 1/16" (1.5 mm) or less. They may be bigger when burning natural gas. An example of how a 1 mm orifice hole used at different gas pressures effects the amount of generated heat is presented below:

It can be seen from the table that at 25 PSI, a propane burner will supply 20 times more heat than a natural gas burner at 4"WC.

The pressure of natural gas in a pipe is very low and its venturi is able to suck in only about 40 % of the needed air into the burner. The burning flame consumes the rest of the needed air from the air that surrounds it. This is the reason why all natural gas appliances have such generous air openings near the burners. This also means that the gas burner may not work too well when placed inside of the smoking chamber when heavy smoke keeps pouring into it. Because of the natural gas low pressure there is no need for a regulator.

Propane gas is flowing out of a regulator at a much higher pressure and is being able to suck in all needed air into the burner, providing that the venturi chamber is located outside of the smokehouse. Propane gas leaving the tank goes to the regulator first, which may be either fully adjustable (0-20 or 0-30 psi) or preset type (10 or 20 psi). The adjustable regulators usually have a large knob for adjustments. All regulators do basically one function: they reduce a higher pressure down to a lower pressure and keep it constant (regulated). There are also propane gas regulators that are preset to 6 ounces of pressure and they are considered low pressure regulators. Although they are preset they may have a small range of adjustment. Needless to say they will supply less heat than a high pressure burner.

A typical propane system

Smokehouse burners

If the smokehouse is small, you are better off installing using an electrical heating element. It will be faster, easier and cheaper. Choosing a gas burner for a large smokehouse presents a little problem. Let's say that on the inside your smokehouse is 36 wide, 2' deep and 6' high, a total of 36 cubic feet. Most gas burners are very short, 4 - 6" and if placed inside will provide heat by the side wall only. Venturi part and the connecting hose should be outside of the unit and you are left with a burner head situated a few inches from the wall. There will be uneven heat distribution in a smokehouse chamber as the heat will go straight up where the burner is placed. You could of course use a blower but that complicates design that we try to keep very simple. What you will need is a long burner like the 32" long burner in the photo in the table above. If the entire burner must be placed inside, replace hose with an iron pipe. Keep in mind that now when venturi is inside it needs air supply. The air may come in the smoke delivery pipe or some opening must be provided.

Using this adjustable length burner it is possible to place burner in the centre of any size smokehouse. Using a simple T connection it is practical to connect a second burner. For more even heat distribution a metal plate (baffle) can be placed above the burner.

Burner Safety Issues

In the USA most burners used in outdoor cooking equipment don't require safety valves. In Europe and in Asia the government guidelines are stricter and the safety valve must be installed. The American school of reasoning believes that in outdoor cooking equipment (propane) when the flame goes out, the gas can safely escape to the atmosphere and the cook will eventually discover the fact. A smokehouse like many other gas heated appliances (ovens, water heaters) present safety hazards. All above appliances make use of a pilot light to ignite the main gas burners. If the flame of the burner or the pilot light becomes extinguished for any reason, the gas will keep on going into the smokehouse creating both a risk of fire and a health hazzard. The risk will deepen even further if the smoke generator will be supplying smoke at the same time as this may deliver a spark to ignite the gas. This is another reason why a smokehouse should have sufficient air draft. The draft will allow gas to burn cleanly and to push the exhaust gases out.

To eliminate this danger a device called thermocouple is used to sense when the pilot light is burning. A thermocouple consists of two dissimilar metals that are joined together at the sensing end. A different voltage is generated, typically between 1 to about 70 microvolts per degree Celsius which increases with temperature. The tip of a thermocouple is placed in the flame and as long as the thermocouple remains hot it holds the pilot gas valve open. If the pilot light goes out, the temperature of the thermocouple will drop and the gas supply valve will close, shutting off the gas to the pilot light. The same thermocouple controls the main gas valve in the same manner. The thermocouple voltage, typically around 20 mV, operates the gas supply valve responsible for feeding the pilot.

Safety valve

These valves house the thermomagnet that provides gas shut down if the safety thermocouple is not heated. There is a connection for a thermocouple, gas supply to a pilot burner and the manual reset.

Burner working fine. The tip of a thermocouple is hot and the thermocouple generates sufficient voltage to keep the solenoid (electromagnet) energized. Solenoid is holding strong the valve and the spring is not strong enough to push it up.

Flame is out. The thermocouple has cooled down and its voltage is too low to keep solenoid energized. The spring pushes the valve up closing gas supply.

To start the burner again we have to open the flow of gas. The thermocouple is cold and the voltage is too low for the solenoid to pull the valve down. Manual reset button has to be pushed down to open gas supply and the pilot can be re-lit. The reset button has to be held down for 20 more seconds to warm up the thermocouple. Now when the thermocouple is hot again, it produces enough voltage for the solenoid to hold down the valve.

Smoke Delivery Pipe

Meat smokehouse needs smoke delivery pipe to supply sufficient amount of smoke. A little smoker may need just a pan with some sawdust in it, but a smokehouse needs more smoke. It is hard to beat the effectiveness of a smoker that is connected to a fire pit with a pipe or a trench in the ground. The distance between them should be about 4-7” (1.2 – 2.1 m) and they should each stand on a different level, with the smoker obviously higher than the fire pit. The pipe (trench) must be covered with at least 2” (5 cm) of soil to provide insulation. The rest depends on the imagination and technical skills of the builder and can involve dozens of different arrangements. Two metal drums can be used (one for the smoker and the other for the fire pit). For the smoker, a simple wooden box will do. The fire pit can be built from bricks, stones, or some other elaborate design.

There is no fixed rule for the length of the pipe. A 4’ - 7’ (1.2 – 2 m) pipe seems to be the preferred length in most installations. An important thing is that it has sufficient draft for the smoke to flow freely. The pipe connecting the fire pit and the smoker should be about 4-6” (10-15 cm) in diameter and made of suitable materials like stainless steel, metal stove pipe, sewer clay pipe, or a concrete pipe, but never plastic. A little incline of 5 - 10 degrees will help direct the smoke into the chamber. Increasing the angle even more is not practical on flat ground because it will require digging a very deep hole to accommodate a fire pit. Placing smokers on a very high base would also require a step ladder.

It is amazing how many designs call for a 12 foot long pipe, yet, they do not provide any reasons for such a length. The feasible explanation would be to cool the smoke down but how can you bring the smoke temperature down to 70° F (21° C) when it’s a baking hot 95° F (35° C) in the shade in Florida? The hot smoke (well over 100° F) enters the pipe where it will remain for a few seconds. Even submerging it in the Gulf of Mexico will not help because the average water temperature is 85° F (30 °C) for about 6 months out of the year. At best you can generate cold smoke at night time in December, January and February when the temperatures drop down to 50° F (10° C).

The same pipe (if made of metal) will be more effective in cooler climates allowing cold smoke generation for most of the year. What about those who smoke in the Northern States, Canada, and Northern Europe? They don’t need a long pipe to cool down the smoke; they may have problems generating sufficient heat to cook the product. An exposed long metal pipe will loose so much heat in winter months that it will have to be insulated. Before we decide on the length of the pipe it would be wise to answer the following questions:

Do we need cold smoke?

Do we want to cold smoke the whole year or just in winter months?

What temperatures can be expected at night time?

In the past the cold smoke problem was solved by building high smoking towers (especially in Eastern Europe) that were 18’ tall. The smoke would come in through a trench from a free standing fire pit outside. The height of the tower induced a lot of natural draft and the smoke was quite cold before escaping the smoking chamber. Bear in mind that the countries in Europe where most serious smoking is done lie in the lattitude of Quebec, Canada, where the climate is much cooler than the rest of continental USA. Similar designs of smokehouses were employed in Virginia in colonial America. For people living in a hot climate the best technical solution is the one we have been using for thousands of years. If you like to use cold smoke, then wait for the winter months. In the summer, you are better off to smoke products with warm or hot smoke.

Pipe material

Any environment friendly material could be used for making pipes, and some of the best ones are listed. Stainless steel, metal, concrete, sewer pipe, clay pipe and stove pipes are all good materials for pipe making. Air conditioning duct pipe is also good, and it comes in different sizes. There is a wide assortment of elbows, reducers, as well as other connectors for those interested in making pipes. It is inexpensive, very easy to work with, and commonly available. It has one drawback; it is made of galvanised steel. To tell if galvanized steel is good for smoking is like trying to decide which came first, the chicken or the egg. It is made of metal sheets that are dipped into a hot bath of melted zinc and some other chemicals. Zinc melts at 787° F (420°C), and boils at 1,665° F (907° C).

Although zinc presents no danger, a metallic element such as cadmium is bad for our health. Determining the exact composition of a particular pipe is difficult. This is why the Food Safety and Inspection Service of the United Stated Department of Agriculture says "Don’t smoke foods in makeshift containers such as galvanised steel cans or other materials not intended for smoking." With every puff of a cigarette, we probably inhale more chemicals than if we had smoked meat for 100 hours with a galvanised pipe. But to keep our conscience clear, we decided to present the official view of our government.

Before smoking for the first time, any section of pipe that makes direct contact with burning wood in the fire pit should be burned with hot fire. This takes care of initially burning away any deposits. The rest of the pipe is exposed to such low temperatures that it can not possibly react with any chemicals that were deposited on its surface during the manufacturing process. Better still, break your pipe into separate sections. The section that makes direct contact with a fire pit can be made of steel, tile pipe, or reinforced concrete, and the rest can be made of galvanised duct.

Smoke Delivery Channel or Trench

Smoke can be delivered by a brick or concrete channel.

Trench

Digging a trench instead of installing a pipe creates a weaker and impermanent design. Nevertheless, for those in a hurry or on a tight budget, it is a viable solution. It can be constructed anywhere, in the woods during a hunting trip or on the beach. Fortunately, there are almost no costs involved. Digging a trench is a very simple matter since the width of the board controls all other criteria. All we have to remember is that the width of our trench including all its dimensions have to be covered by the board.

A good trench is 8” wide by 11”deep ( 8” for the trench channel and 3” for the soil cover). The first dimension is crucial because the trench will be covered by a wooden plank 12” wide and 6 – 8’ long, a size usually stocked by building supply stores. A gap of at least 1 ft is needed between the fire pit and the beginning of the wood channel to eliminate the possibility of flames reaching and burning the wood boards. This gap is covered by a metal plate or a concrete slab measuring about 18”x18”, available in any hardware store. Now we can cover everything with at least 3” of soil. In the wilderness, we have to find a suitable rock that will perform the same task.

The trench should rise 1” per foot, atop the fire pit creating a 5 degree angle. Instead of a wood plank, four concrete slabs may be used, as long as they touch each other and prevent soil from falling between them. They come in different sizes, most often square and ranging from 12 inches to 18 inches and about 2” thick. A trench dug out in sandy soil will need some gravel and small rocks to reinforce it, or its walls may start to collapse.

Diffuser

A nice finishing touch is the installation of a smoke diffuser which is a galvanized metal box, 1 foot (30 cm) square and 2 feet (60 cm) high, open at the bottom. Three-quarter-inch (19 mm) holes are drilled or punched in the sides and top to permit the escape of smoke. The diffuser is placed over the mouth of the elbow and allows for an even distribution of smoke throughout the smokehouse.

Wind

In mountains or windy areas it is a good idea to place a fire pit in a position where the smoke will follow the direction of the prevailing wind. For instance, if the wind blows from the south to the north, the fire pit should be placed south of the smoker. In this manner, we no longer fight against the wind but use it to lead smoke into the chamber.

Smokehouse Baffles

Flame and heat protection is a big problem for small smokers since the distance between the fire pit and the hanging meats is so short. That is why smaller smokers must have a safety feature called a “baffle” built into it to prevent this kind of scenario. Most often a baffle is some type of a perforated metal plate that physically separates the fire pit from the smoking chamber.

There are two kinds of baffles:

Directional baffles

Safety baffles

A directional baffle is a solid metal plate whose purpose is to direct heat and flames into a specified direction. The directional baffles could be installed vertically, horizontally or a combination of the two. Directional baffles are used most often in wood stoves. Directional baffles are presented in the chapter on fire pits.

A safety baffle, commonly used in one unit smokers, is a perforated metal plate that separates the firepit from the meat compartment and its main purpose is preventing flames from reaching the smoke chamber. Better designs advocate the use of two or three baffle plates separated by 3 - 4 inches, though that complicates the smokers construction and steals the valuable space.

Baffles are a very important design feature of any small smoker with a fire pit located in its bottom part as they safeguard products from flames and wild jumps of temperature. They provide a piece of mind when smoking making the entire process more organized and controllable and they also help to disperse smoke slowly and evenly to all parts of the smoking chamber. If a smoker is connected by a pipe with a separately standing fire pit, the baffles are not necessary.

Meat hangs in different sections of the chamber but the smoke pouring out of the pipe, or the one raising up from the fire pit is using the path with the least resistance and that means it is rushing straight up. A baffle puts some brakes on the smoke forcing it to slow down and disperse evenly in all sections of the drum. During cooking the baffles will slow down the heat escaping straight up and the design of the smoker will be more efficient.

A baffle is a perforated metal plate, rectangular or round, of about 1/8” (3 mm) thickness or more, strong enough to support the weight of river gravel or another baffle. Its diameter should be about 2” (5 cm) smaller than the diameter inside of a barrel to facilitate removal for cleaning. The holes between ½ - 1” ( 12 – 25 mm) diameter should be drilled at random so if the two baffles are used, there will be some offset between holes for better smoke distribution.

The smoker will work even better when a second baffle is installed. The bottom baffle will rest freely on three right angle metal supports secured to the barrel with bolts and nuts and positioned every 120 degrees. The top baffle will also rest freely on three spacers, about 4” high and also placed every 120 degrees.

Single baffle

Two baffle plates with spacers

Overlapping plates baffle. You may use two solid 1/8” overlapping plates and the size should correspond to about 60 % of the depth of the smoking chamber. The top one should be 4” higher than the bottom one and will overlap it by 4”.

Gravel baffle. One of the easiest, most effective baffles can be made by placing medium size river gravel on a suitable screen. Gravel baffle placed on top of smoke delivery pipe.

Smokehouse Draft

Meat smokers and smokehouses need draft. The draft is the sucking action of your smoker, it’s pulling power that allows it to draw air into the fire pit for combustion and then pushes smoke into the smoking chamber. At the same time, it removes gases from the smoker through the exit opening, be it a stovepipe, chimney, or simply a hole in the top cover. In more sophisticated terms it is the pressure difference between the surrounding air of the firebox and the gases in the chimney. The higher the structure, the stronger the draft. Masonry built smokers may include a chimney. However, this is more for looks than practical value because smokers work at rather low temperatures compared to other heating devices, which require more draft.

Although smokers will produce smoke even with very little draft, the importance of this draft cannot be understated. It is needed to suck out moisture and soot laden smoke that remains under the smoker’s cover. Dry wood contains 20 % moisture, and combined with the excess air that enters the smoke chamber and the chimney, we would have to raise the chimney temperature to almost 180° F (82° C) to prevent condensation, which would dry out our meat pieces or sausages. The right amount of draft solves the problem.

Smoking on uneven ground already creates some draft because one end of the pipe will be higher than the other. Factors like chimney height, flue size, altitude, and the wind blowing over the chimney all contribute to the draft effect. Nevertheless, the single most contributing factor is the temperature difference between the outside air and the flue temperature. This is why every smoker or wood stove operates better in cooler winter months than in the warmer days of summer.

Some simple smokers are made from concrete blocks loosely arranged together and the smoke tunnel (about 3 feet long) is on the same level as the smoker. An old potato burlap sack is placed on top to control the smoke. The moment the air is warmed up, it goes straight up, and cold air takes its place creating a natural draft. This works fine for the simplest of the smokers, but once accessories like baffles, supports, smoke sticks, hanging meat, and elbows in a pipe are added to the design, the smoke may need some extra sucking power (draft) to go up the chimney.

Note: draft does not depend on the length of the pipe but on the difference in pressure (height) between the fire pit smoke outlet level and the smoke inlet level in a smoker. A shorter steep pipe can create a stronger draft than a longer one with a smaller angle as shown in a drawing below.

In the above drawing, pipe B is shorter than pipe A but it has a bigger angle and more draft. For instance, to achieve a 30 degree angle with a 10’ (3m) pipe, the smoker’s base has to be placed 5 ft (1.5 m) higher than the fire pit.

It is possible, however, to achieve a bigger angle and more draft by taking advantage of mountainous terrain.

Draft can be increased by:

increasing the height of the smoke

increasing the lenghth of the smoke exit pipe

increasing the angle of the smoke delivery pipe

insulating chimney or smoke exit pipe

What do we do if our smoker is not pulling out smoke? We could place our fire pit 2’ under ground, but that would require running a connecting pipe or making a trench. In both cases we have to dig and if our construction rests on a concrete surface it looks like a problem. Not really, all we have to do is to add 2’ of a metal pipe of 6” diameter to the top of our smoker and the problem is fixed. Or we can increasing the height of the smoker by laying an additional level of blocks.

Draft controls

Controlling smoke draft is of utmost importance when smoking meats. It is accomplished by installing a damper in a stovepipe, installing a smoke stack with a built-in damper, lifting up the smoker’s cover, adding or removing burlap bags, covering open holes in the top cover, or any other means that we have at our disposal.

There isn’t a standard solution because there are so many different smokers. The two main reasons to control smoke are as follows:

It has to be fully opened to warm up the smoker (before the smoke is applied) to get rid of moisture

To control smoke outflow when smoking

A smoker is not a wood stove whose purpose is to warm up the house or boil the water and its temperature expectations run much lower. That also means that there is no need to create an extremely strong draft. Once we start cooking meats inside the smoker and the temperatures are higher, draft becomes much more important. You also need more draft if you intend to burn wood cleanly and efficiently. The easiest device to control draft is a flat damper which is basically a flat piece of metal. This simply slides in and out of a slit in the stove pipe or brick chimney

An adjustable opening is needed in the centre of the smoker’s cover to let this moisture out. Any cover will do, even cardboard can be raised an inch or two to let the smoke out. Smoked meats need a supply of fresh air that brings some fresh moisture with it. It also depends on the climate. In dry air, smoking will have a tendency to prematurely dry out the sausage casing. Once it is dry on the outside, it becomes more difficult for the smoke to diffuse into the meat.

A fire pit does not have to be totally sealed and enclosed when smoking. If smoke is coming out of the smoker, that means that the fire pit is doing its job. Once smoking is complete and we decide to continue cooking meats inside the smoker, enclosing and insulating the smoker and fire pit become more important. A little conical shield on top of a smoke exit pipe will give it a nice touch. At the same time it also protects the pipe from rain and also serves as a spark arrester. There is no preferred fixed diameter for a smoke exit pipe but a six inch (15 cm) pipe seems to be the unwritten standard.

Humidity in a Smokehouse

There are some expensive factory made smokehouses that permit humidity control. Most smaller factory made smokehouses cannot even produce cold smoke and humidity control is out of the question. Regulating humidity in a home made smokehouse can be done indirectly, and is relatively simple and cost free. What is required is a fair understanding of a smoking process and humidity behaviour.

A particular climate and ambient temperature are the most important factors that a smoker must learn how to manipulate. Thus when smoking in a home made smokehouse the humidity can be controlled by:

choosing the time of the smoking

placing a water filled pan inside the smoker

using moist wood chips or sawdust

The amount of needed humidity is dictated by:

type of a product - hot smoked sausage, cold smoked sausage, smoked and air-dried ham, or just air-dried ham

the smoking method that will be employed - cold smoking, hot smoking

Geographical location plays a crucial role here. There is more humidity in areas containing a lot of water like lakes, rivers or the sea shore. Arid areas like deserts or mountains have less water and subsequently less humidity. If you live in the Eastern part of the USA or Gulf states, you have a lot of humidity. If you live in the West (Arizona, New Mexico, California) you get less of it. As you cannot change the physical location of the smokehouse, you have to learn how to go around it and how to choose the time of smoking to your maximum advantage.

The most important rule to remember that when the temperature goes up, the humidity goes down. When the temperature goes down, the humidity goes up (night). That holds true when the weather is relatively stable or when smoking inside. When the clouds come in and it starts to drizzle, the humidity will go up immediately.

Different smoking methods require different humidity levels:

cold smoking - 75 - 85 %. It is important to employ high humidity levels when cold smoking.

warm smoking - 50 - 70 %. It is advisable to start smoking at high humidity levels.

hot smoking - 40 - 50 %. In case of hot smoking which is a relatively short process (about 2 hours), humidity control is of secondary importance.

In dry climates like New Mexico or Arizona the relative humidity stays low at 15 - 20 % during day time and it will not be advisable to smoke meats at such conditions. The meat will prematurely dry out. The remedy will be to place a water pan inside of the smoker and moist wood chips. The best solution is to smoke at night time when the temperature will drop and the humidity will increase.

An often heard complaint when smoking in outside smokehouses is that the meat is wet on the surface and the final product tastes sour. In most cases it is a humidity problem. Outside smokers in most cases have a free standing firebox that is connected to a smoker by a dug in trench or pipe (clay or metal). After rain the ground is soaked wet and this moisture will travel with smoke together. The remedy is to heat up the smokehouse well so that the moisture will evaporate away. Another problem is that when smoking in a popular metal drum at very low temperatures there might be a case that the smokehouse temperature will be lower than the temperature of the entering smoke. Moisture from the outside or even moisture from the wood or the meat itself will condense on the walls of the drum. Then it will combine with soot and other unburnt particles and will start condensing on the meat or sausages. That of course will affect the color of the product and even worse, it will impart a soury flavor to the finished product. The solution is to insulate the drum on the outside with some material and heat up the drum before smoking.

Note controlling humidity levels is very important for commercial manufacturers who produce thousands of sausages a day. Proper humidity control during production and storage will decrease meat loss and will increase profits. It is of lesser importance for a home smoker unless he is making fermented sausages.

Humidity Measurement

Manufacturers of industrial quality humidity sensors that could be inserted into a smokehouse can be located on the Internet although the prices are rather steep.

Dry and Wet Bulb Method

Traditionally humidity was measured by the dry and the wet bulb method. The dry-bulb is a common mercury/liquid thermometer to measure the air temperature. The wet-bulb is a second mercury/liquid thermometer whose bulb is covered by a muslin bag which is kept moist. Both thermometer readings are taken and the difference between them allows us to calculate the humidity using tables.

Before the reading is taken the muslin bag that covers bulb of the wet bulb thermometer must be moistened by dripping it in clean water. Then the thermometer is inserted into the smokehouse and after about 30 - 60 seconds the reading is taken. At the same time the temperature of the dry bulb thermometer is also taken and the difference from both readings is obtained. Then the table is consulted to determine the relative humidity. This procedure is explained in details below in the Dry and Wet Bulb Method. The thermometers should be placed horizontally on the same level. If they were placed vertically with the wet bulb thermometer below the dry bulb thermometer, we could obtained incorrect readings as the smoke and air would be cooled by the evaporation of moisture on the wet bulb. It can easily be determined from the wet bulb and the dry bulb tables that the flow speed of the smoke will influence the reading. The slower the flow rate of the smoke, the smaller the difference in temperatures and the higher the relative humidity. The faster smoke flow, the lower relative humidity and the faster drying (moisture removal) from the smoked product.

The simplest hygrometer known as "a sling psychrometer" can be made from two thermometers attached (tape, string or wire) to a wooden board and the mercury or liquid filled ends sticking over the edge of the board about 1" (2.5 cm). This thermometer is called the dry-bulb thermometer.

The second thermometer has a wet cloth (gauze, muslin bag) around the thermometer bulb, and secured with the rubber band or other ways, This thermometer is called the wet-bulb thermometer.

The fan is needed to blow the air on the thermometers until both temperatures will stabilize and the readings are taken. Water will evaporate from a little bag cooling the wet-bulb thermometer

The temperature readings are taken and substracted to get the difference.

The humidity table is consulted. Find the dry thermometer temperature in the row on the left, then find the difference between two temperatures in the column on the top. Follow the air temperature to the right and follow the difference in temperature column down. The point where the row and column intersect is the relative humidity. The examples follow below.

A better model can be made by drilling a hole in the top of the board and attaching a handle with a rope or a short piece of chain so that the whole assembly can be whirled around (no fan needed now). During the whirling, the water evaporates from the wick, cooling the wet-bulb thermometer. For the most accurate reading, swing your psychrometer for several minutes, until the thermometer wrapped in cloth gives a constant temperature reading. If the ambient air is dry, more moisture is removed from the bag or wick, cooling the wet-bulb thermometer more and the temperature difference between two thermometers will be greater. The wet-bulb thermometer always gives lower readings than the dry-bulb because of the cooling effect of moisture evaporating from the muslin bag. If the air is very humid the difference will be smaller. If the relative humidity is 100 %, there is no difference between the two temperatures.

Relative Humidity Table

The following table is just a small section of the complete humidity tables:

Note Numbers in blue colour denote relative humidity.

Example 1

Dry bulb thermometer shows reading of 70° F and the wet bulb thermometer shows 60° F. Find the relative humidity. The difference between readings is: 70 - 60 = 10° F. Following 70° F dry bulb temperature to the right and 10° F difference between dry bulb and wet bulb temperature down we can see that they intersect at 55 % relative humidity.

Example 2

Dry bulb reads 76° F and the wet bulb reads 62° F. Find the relative humidity. The difference is 76 - 62 = 14° F. Following 76 °F dry bulb temperature to the right and 14° F difference column down we can see that they intersect at 44 % relative humidity.

Smokehouse Thermometers

Thermometers are one of the most important parts of your smokehouse. The process of both smoking and cooking greatly depends on them. There is no way to determine the temperature inside the chamber simply by looking at the smoke, touching the drum, or inserting your hand into the smoker, no matter how experienced you are. It can be compared to forcing a blind man to shoot a free throw. When using a thermometer for the first time, most experienced individuals say they don’t understand how they have been working so long without one. Well, one explanation is that for a long time they were not easily available in countries outside of the USA that were damaged by war. It turns out that these very countries are the ones with the longest tradition in smoking. Today, there is no excuse for not having one. The thermometer with the longest stem, 12” (30 cm), works best. When mounted on top of a smoker, it will read the temperature of the area where the meats are. It doesn’t have to be permanently mounted. As long as there is a suitable hole, it can be inserted to determine meat temperatures, and can be removed when the smoking is finished.

Another thermometer is needed to read the temperature inside the meat while cooking. When the meats are smoked, they have the proper flavor and color, but they are still raw and need to be cooked inside a smoker or poached in water. In both cases a thermometer is needed to indicate when the meat has reached a safe internal temperature. This thermometer has a long temperature resistant cable. On one end there is a probe that we insert into the cooked product and on the other we have the dial indicator, or electronic display that is kept outside.

It is advisable to have a thermometer with a built-in sound alarm that would warn us when we have reached a pre-set temperature.