Diesel exhaust fumes

Diesel exhaust is produced by the combustion (burning) of diesel fuel. The exhaust is a complex mixture of gases, vapours, aerosols, and particulate substances. The exact nature of the exhaust depends on a number of factors including the type of engine, how well serviced / maintained the engine is, type of fuel, speed and load on the engine, and emission control systems.

Diesel exhaust may contain:

• Carbon (soot)

• Carbon monoxide

• Carbon dioxide

• Oxygen

• Water vapour

• Nitrogen

• Oxides of nitrogen (e.g., nitrogen oxide, nitrogen dioxide)

• Oxides of sulphur (e.g., sulphur dioxide)

• Alcohols

• Aldehydes

• Ketones

• Hydrocarbons

• Polycyclic aromatic hydrocarbons (PAHs)

• Diesel particulate matter (DPM)

The most immediate hazard in diesel exhaust is carbon monoxide. See the Carbon Monoxide section for information on how to recognize and deal with carbon monoxide hazards. 

Health Effects of Diesel Exhaust Fumes:

Short term exposure to diesel exhaust can cause coughing, and irritation of the eyes, nose, throat, and respiratory tract. Breathing in diesel exhaust can cause lung irritation and/or an allergic reaction causing asthma (wheezing and difficult breathing), or making pre-existing asthma worse.

Very high levels can lead to asphyxiation from carbon monoxide poisoning.

Long term exposure may lead to serious health effects. The International Agency for Research on Cancer (IARC), which is part of the World Health Organization (WHO), classified diesel engine exhaust as carcinogenic to humans (Group 1), determining that exposure to diesel exhaust emissions increases the risk for lung cancer and possibly bladder cancer.

How to Recognize Diesel Exhaust Hazards:

Running any diesel engine without adequate ventilation is a hazard. Exhaust emissions from diesel engines are usually more visible than those emitted from petrol engines because they contain over ten times more soot. In general, diesel engines produce less carbon monoxide than petrol engines but more oxides of nitrogen, sulphur oxides, aldehydes and particulate matter.

Risk Assessment of the Level of Exposure to Diesel Exhaust:

• Have there been any ill-health complaints from potentially exposed people? If yes, what has been done about it?

• Is the engine being operated at full speed or left idling? What is the purpose of running at idling speed or full speed. Can it be avoided?

• What is the state of the engine? Can the engine efficiency be improved, and can operating times be reduced? Improving the efficiency of the engine will also bring financial benefits.

• What happens to the exhaust emissions: do they enter directly into the workplace, or are they piped away or processed through a treatment system?

• Is there visible smoke near the exhaust point? What is the type of smoke, ie white, black or blue? How could it be avoided? Is there a visible haze in the workplace? Can it be avoided and how?

• What controls are in place? Are they satisfactory?

• Are there soot deposits in the workplace; how significant are they?

• How many engines are running at any one time? Are they all necessary?

• Is it necessary to use diesel engines, or can alternative power sources be used?

Action Plan if Hazard is Believed to be Present:

• Identify the source

• Ventilate work area

• Eliminate by replacing diesel powered engines with electric or other types of power sources (remember to manage any risks introduced by alternative power sources).

• Use alternate fuels where possible.

• Use low-emission engines.

• Use exhaust treatment systems such as filters, catalysts and/or converters, and a corresponding maintenance program.

• Run engines outdoors (instead of indoors).

• Maintain engines to help with their efficiency.

• Maintain the body of the vehicle to make sure that exhaust is not leaking into the cab or passenger area.

• Modify the layout of the work area to separate the area where people must work and areas where exhaust is generated, such as isolate the generator in a separate, ventilated space, or isolate the worker in a sealed, air conditioned cabin (air filtered) where possible.

• Ventilate appropriately, such as providing positive pressure ventilation, exhaust extraction devices, inlet and exhaust general (dilution) ventilation, and/or local exhaust (such as tailpipe hose exhaust).

• Education and training to workers about the exposure to diesel exhaust and proper use of control measures.

• Turning off engines whenever possible.

• Use of personal protective equipment, such as respirators, only if there is sufficient oxygen present.

More information can be found at:

Operations Portal - Carbon Monoxide Hazards

UK Health and Safety Executive - Control of Diesel Exhaust Emissions

Canadian Centre for Occupational Health and Safety - Diesel Exhaust 

OSHA - Diesel Exhaust