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.
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.