Lab Safety

All content from Flinn Lab Safety

Safety Culture

Always perform a risk assessment before performing an experiment or demonstration.

Duty of Care

Teachers owe their students a duty of care which means we must instruct and warn, supervise, and ensure a safe learning environment.
Negligence includes the failure to warn students of foreseeable risks.

Creating a Safety Culture

The same, tragic laboratory accidents recur annually.
We should always perform research into the hazards associated with experiments or demonstration before carrying them out. This can include searching the internet (be careful to verify the credibility of the source) and reading safety data sheets and chemical labels.
Safety should be discussed consistently during the school year, at least every time you begin a lab, so that safety’s importance is inculcated in students.

The Most Commonly Reported K-12 Laboratory Accident

Causes of Laboratory Accidents

When doing demonstrations like flame tests to observe electronic transitions in cations never pour methanol or other flammable solvents on burning flames. Instead, cap the bottle and remove from the demonstration area and let the flames burn out or cover them with borosilicate glass petri dish covers.
Always perform a risk assessment before performing an experiment or demonstration.

Flammable Liquid Safety

Many flammable liquids are hazardous by inhalation and skin-contact. Thus, proper personal protective equipment such as gloves and chemical-splash goggles should be worn while handling flammable liquids, and they should be used in fume hoods.

Flammable liquids tend to have high vapor pressures and can have high densities relative to air. Thus the vapors can travel along bench tops and encounter sources of ignition. For this reason, flammable liquids should not be kept or used in the presence of ignition sources such as hot plates and Bunsen burners.

Using Chemical Labels and Safety Data Sheets

It is a good idea to read the chemical labels and Safety Data Sheets for any chemicals used in demonstrations or experiments before you carry them out with students.
Chemical labels and Safety Data Sheets convey hazard and personal protective information about chemicals in a templated format that is meant to be accessible and unambiguous.
You can access free safety data sheets using the Flinn Scientific database: https://www.flinnsci.com/sds/

Principles of Toxicology

Acute toxicity, which is defined as the immediate effect of a substance as a result of a single dose, can be measured experimentally. Chronic toxicity, resulting from low doses of a chemical repeated over longer periods of time, is more difficult to test and is usually evaluated based on epidemiological evidence.
In general, chemicals with LD50 values less than 300 mg/kg are considered highly toxic, those with LD50 values between 300 and 1,000 mg/kg are considered moderately toxic, and those with LD50 values between 1,000 and 5,000 mg/kg are considered slightly toxic.

Practicing strict chemical hygiene is thus the most effective way to reduce the hazards and work safely with chemicals. This includes always wearing goggles, gloves, and other personal protective equipment; working with volatile substances only in a properly functioning hood or well-ventilated lab; immediately cleaning up all spills, and not eating, drinking or chewing gum in the lab.

Preventing Exposure: Personal Protective Equipment

Goggles

Chemical-splash goggles should be worn during any experiment or demonstration in which chemicals or heat are being used. These should conform to the ANSI standard D3.
The “acid in the eye” demonstration, in which acid is dropped onto an egg white to denature and discolor the proteins is a more visceral way to convey to students the importance of wearing their goggles during lab.

Gloves and Proper Attire

Gloves should be worn when working with contact hazards. Latex gloves are inexpensive, but if students are allergic nitrile gloves are a great alternative.
Students should wear long pants and closed-toed shoes to lab, tie long hair back, and wear a lab coat or apron when handling certain contact hazards such as concentrated acids.

Common Lab Equipment

Hot Plates

Never heat mixtures to dryness, i.e. do not boil away all of the solvent (typically water) in a beaker or flask because this leaves the vessel to absorb all of the heat and will result in the vessel cracking or fusing to the plate surface.
Be careful when removing items from hot plates, use tongs or insulated gloves if necessary and let things cool on ceramic pads to avoid damaging lab benches.
Do not heat flammable liquids on hot plates.

Bunsen Burners

Do not heat flammable liquids with Bunsen burners.
Clamp test tubes and crucibles to ring stands while heating so that you do not have to hold them near a flame with test tube holders. Be sure that the clamps are not coated in rubber because it will melt.
Use Bunsen burners only with house gas lines, as opposed to portable propane tanks.
Remember to shut the gas off when burners are not in use.

Borosilicate glass has a lower thermal expansion coefficient than regular glass which makes it less likely to crack or fracture owing to the expansions and contractions materials go through when subjected to temperature gradients.

Common Lab Practices

Acid Safety

Concentrated acids are strongly corrosive to all body tissue, especially eyes and skin. Concentrated hydrochloric and acetic acid are also toxic by inhalation. You should wear appropriate PPE when using acids and use inhalation hazards, such as glacial acetic acid, in fume hoods.
Always add acid to water when performing dilutions to minimize the amount of heat evolved during the dissolution process.

Safety in Inquiry Labs

If students will be using small quantities of acid, have them dispense from small bottles as opposed to large, heavy 2.5 L bottles, which are more difficult to control.
Inquiry investigations are generally divided into two main categories or levels depending on whether it is the teacher or the student who (a) generates the “question” or purpose of an experiment and (b) develops the procedure to answer the question.
Students should carry out a hazard assessment as part of any inquiry lab. This requires that students identify the nature of all possible hazards, evaluate their relative risk, and write safety precautions and procedure steps to protect against the hazards and minimize the risk. The teacher must verify all of this information in writing before students may begin an investigation.
Teachers should train students in the use of Safety Data Sheets and chemical labels. These materials provide essential information concerning the physical and health hazards of chemicals and the safety precautions required for their use. These should be included with the written procedure to be reviewed by the teacher.

Spill Control

Purchase and store highly toxic or reactive substances in secondary containment devices, such as Chem-Saf™ bags (heavy-duty plastic bags) or Saf-Stor™ cans (metal paint can) so that if any leaks occur they are contained and do not become spills.
Purchase, store, and dispense chemicals from the smallest bottles possible.
Effective spill control materials include three components—sand, an absorbent agent, and a neutralizer. Spill control materials should be capable of handling a spill from the largest bottle in a storage room or lab, which is usually a 2.5-L acid bottle. Sand is used to surround and contain a spill, provide traction, and prevent the spill from spreading across the floor. An absorbent is added to contain and absorb spilled liquid so it is easier to clean up, transport, and dispose of. Neutralizer, usually sodium carbonate or calcium hydroxide, is used to neutralize inorganic acid spills. If concentrated bases such as ammonium hydroxide solution will be used in the department, it is a good policy to keep citric acid on hand to neutralize bases.

Written Spill Control Procedures (Chemical Hygiene Plan)

Assess the spill, its hazards, and danger to students.
Notify personnel and evacuate if needed.
Immediately attend to anyone who made contact with the spill.
If volatile, ventilate and evacuate.
If flammable, remove all ignition sources.
Gently sprinkle spill with spill neutralizer/material.

Chemical Treatment and Disposal

Chemical Disposal and Resource Conservation and Recovery Act

The Environmental Protection Agency (EPA) recognizes three classes of hazardous waste generators, based on the amount and kinds of hazardous waste generated in one month. The storage and reporting regulations become increasingly stringent as the amount of hazardous waste increases. Schools that generate less than 100 kg (220 lbs.) of hazardous waste per month, and no more than 1 kg of acutely hazardous waste in any month, would fall into the least regulated, “conditionally exempt small quantity generator,” class. Your school very likely falls into this category.
P-listed, or acutely toxic, wastes are especially important because any school generating more than 1 kg of acutely hazardous waste per month will be subject to the most stringent generator requirements for listing, storing, and reporting all their hazardous waste.
Make sure that you have effective chemical purchasing and inventory controls in place if you use P-listed chemicals. This will prevent your school from accumulating excess chemicals that must be discarded.
An accurate and up-to-date chemical inventory is the most effective means of preventing the accumulation of unused chemicals that will need to be discarded. This is especially important for discarded chemicals that would be designated as P-list, or acutely toxic, hazardous waste

Flinn Disposal Methods

The EPA and many states provide several regulatory exclusions that allow generators to treat hazardous waste without a permit as part of a broader mandate to reduce waste. These include the domestic sewage exclusion, elementary neutralization, recycling, treatment in accumulation containers, and burning in small boilers.
The Flinn Science Catalog Reference Manual, provides detailed instructions for treating chemicals prior to disposal down the drain or the regular trash to minimize hazards.
Always read the full disposal method procedure and make sure you are comfortable with the chemistry involved before performing a treatment. Also, be sure to follow any local regulations.

Characteristic Waste

Characteristics- ignitability, corrosivity, reactivity, and toxicity.

Reactive Waste

May react with water, give off toxic gases, capable of detonation, or explosion (under normal circumstances or when heated).

Fume Hoods, Eyewashes and Safety Showers

Lab Ventilation and Fume Hoods

A fume hood should be used if the Threshold Limit Value, or TLV, of a chemical is less than 50 ppm. Examples include hexane, toluene, naphthalene, glacial acetic acid, and aqueous solutions of pure halogens. All labs from Flinn will specify when the use of a fume hood is required for experiments.
To measure the air flow in your hood a velometer can be used. This device measures air velocity with readings expressed as linear feet of air per minute. To check hood efficiency, measure the air velocity at the “face” of the hood opening, ideally at multiple locations across the face. A hood should provide air movement of at least 100 linear feet of air per minute.

Safety Showers and Eyewashes

OSHA safety regulations require every science laboratory that handles chemicals should be equipped with an eye wash station and a safety shower. These items must be ADA compliant. The OHSA regulation states “Where the eyes or body of any person may be exposed to injurious corrosive materials, suitable facilities for quick drenching or flushing of the eyes and body shall be provided within the work area for immediate emergency use.” This means the eye wash and safety shower must be in the laboratory classroom, not in an adjacent room. The water temperature delivered by emergency equipment should be “tepid”, which means it should have a temperature of 60 to 100 ºF.
Both eyewash stations and safety showers should be tested regularly. Sometimes calcium deposits can collect on the heads and these should be carefully removed with a brush. Water should be run for a few minutes to ensure it is still coming out clean. Safety inspection tags should be attached to all emergency safety equipment to keep an accurate record of testing.

Fire and Fire Extinguisher Basics

You are not required to fight a fire. If you have the slightest hesitation about your safety, the safety of your students, or your ability to fight the fire, do not attempt to extinguish the fire—simply get out, pull the alarm, start an evacuation of the building, and notify the fire department.
Have you been trained on how to properly use a fire extinguisher? The time to learn is before an emergency occurs! Ask your local fire department to provide hands-on training on how to use a fire extinguisher. In most cases, the company that furnishes and inspects the fire extinguishers at your school will provide extinguishers at no charge for this purpose. If you have never been trained in using a fire extinguisher, evacuate the room immediately. Do not fight the fire.

Fire Triangle: Fuel-oxygen-heat

P.A.S.S:

P: Pull the pin.
A: Aim the extinguisher nozzle.
S: Squeeze the lever
S: Sweep from side to side (at base of fire).

Fire extinguishers should always be within 25 feet of science labs.

Chemical Storage

Compatible Families

Keep an accessible inventory list (purchase date, name of chemical, quantity present, and initials of use).
Flammable cabinets should be made of thermally insulating wood to prevent the contents inside from igniting during a fire. Acids should be stored in all-wooden acid cabinets to prevent corrosion of metal by acid vapors.
To avoid overcrowding in the acid cabinet, purchase small quantities based on your needs.
Never store nitric acid, which is a strong oxidizing agent together with acetic acid. Nitric should be stored in its own compartment.
All chemicals should be kept in a locked storeroom, and an up-to-date inventory should be accessible by any users of the storeroom.
Acetic acid should never be stored with nitric acid.

Stock and Prep Room Design

The stockroom should contain approved flammable liquid and acid storage cabinets. Any free-standing shelving should be firmly secured to the walls to prevent possible tipping. Shelves must have a lip on the front to prevent bottles from rolling off. It is very important that chemicals are not stored more than 6 feet above the floor.
The stockroom should be kept locked and accessible only to authorized users.
OSHA-regulated ventilation sequence requires 6 air changes per hour.

Floor: sealed concrete or double-tile.
Walls should be fire-rated.
Doors should be fire-rated and solid core.
Room must be labeled (NFPA diamond).
Landline installment is recommened.

Lab Safety in American Schools

Lab safety is not part of the curricula at colleges and universities; thus it falls on teachers to seek training and educate themselves on how to provide a safe lab environment for students.
Always carry out a hazard assessment prior to performing experiments or demonstrations.
The most widely reported lab accident in K-12 schools results when flammable liquids are poured on burning flames. Flammable liquids should never be poured on burning flames during flame test demos.
There are simple things you can do to promote a safe lab environment: read chemical labels and SDS, train students how to read labels and SDS, emphasize the importance of lab safety prior to every lab, and wear the appropriate PPE when using heat and chemicals.

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