Carbon monoxide in breathing air during air compressor use

Compressed air can be used to supply clean breathing air to respiratory protective equipment.

However, there is a risk that the air supplied by compressors powered by internal combustion engines can be contaminated with harmful gases and substances, including carbon monoxide.

What is carbon monoxide and what harm  can it cause?

Carbon monoxide (CO) is a poisonous gas  emitted by operating petrol and, to a lesser extent, diesel powered engines. Because  CO is colourless, tasteless and odourless, it has the potential to go  undetected. When CO is breathed in, it prevents the blood from carrying oxygen  to cells, tissues and organs.

While most people can tolerate small  amounts of CO without noticeable ill effects, they may not realise they have  suffered harm until more severe symptoms occur such as headaches, drowsiness,  irritability, reduced judgement and motor skills, convulsions, unconsciousness,  coma and death. Exposure to high levels of CO can be life-threatening.

How can carbon monoxide levels in  breathing air increase during air compressor use?

When air compressors powered by an internal  combustion engine continue to operate when overheated, there is a risk of the  engine oil burning and producing excessive amounts of carbon monoxide. More  specifically, oil lubricants in air compressors may break down at high  temperatures and produce dangerous levels of carbon monoxide.

How can the risk of carbon monoxide  poisoning from air compressor breathing air be managed?

Requirements for air quality from compressors  for supplied air respirators must meet the standard in AS/NZS 1715: Selection, use  and maintenance of respiratory protective equipment. AS/NZS 1715 defines acceptable air quality, air temperature,  concentrations of oxygen, carbon monoxide, carbon dioxide, stale air and  moisture and pressure for supplied-air respirators.

Alternatively, an air compressors intake  may draw air that is contaminated by exhaust emissions from the engine or  another nearby source.

Where an air compressor is used to  supply breathing air at a workplace, the person conducting the business or  undertaking, or the person who has management or control of the workplace,  should:

• Supply  a breathing air system that is designed for safe use with supplied-air  respirators.
• Periodically  test the air quality. This should include installing a continuously operating  carbon monoxide monitor equipped with an alarm on oil-lubricated compressors in  a position as close to the user as practicable.
• Where  available from manufacturers, install a high temperature protection cut off  switch on oil-lubricated compressors.  The high temperature protection cut off circuit should be connected in  such a manner that it is fail safe.  For  example the compressor will not start if there is a wire disconnected or a  sensor fails.
• Place  the compressor air intake well away from sources of contaminants, particularly  exhaust gases from operating plant, equipment or vehicles, or areas where  exhaust fumes may accumulate.
• Establish and maintain a comprehensive respiratory protection program which includes information about how to safely manage sources of air for air-supplied respirators.
• Perform  scheduled, periodic inspections and maintenance by a competent person on all  equipment to ensure it is continuously maintained in safe operating condition.  For example:
• carry  out a daily visual inspection of RPE and breathing  air systems, including the compressor, to identify potential problems
• fix  any identified problems immediately or remove the faulty equipment from service  until it is repaired
• schedule  maintenance in accordance with the manufacturer's instructions
• calibrate  carbon monoxide monitors as recommended by the manufacturer.
• Develop  and implement written safe work procedures that provide workers with adequate  information about the hazards and risks related to the work and the control  measures implemented. This should include information on:
• risks  associated with the use of compressed air for breathing air
• selection,  use and maintenance of RPE and breathing air  system
• use  and maintenance of alarms and monitors.

Further information

For further information about supplied-air  RPE and requirements for ensuring safe breathing  air see AS/NZS 1715: Selection, use and  maintenance of respiratory protective equipment.