BREATHING
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Air Quality Monitors

To verify that breathing air met the requirements of the specification for Grade E breathing air as described in Compressed Gas Association G-7.1, you would have to measure oxygen, carbon monoxide, carbon dioxide, condensed hydrocarbons, and water vapour. These measurements are normally taken by sending an air sample to a lab or by on-site stain tube testing. Laboratory analysis and stain tube tests are made on periodic basis as "grab samples" since continuous testing of this type is impractical.

However, two of the major contaminants, water vapour and carbon monoxide, are often continuously monitored. Although water vapour alone is not hazardous to health, excessive levels can cause failure of breathing apparatus and damage to equipment. Since even small amounts of carbon monoxide within the compressed air stream can have serious consequences, it should be monitored continuously.

Moisture Monitor
Recently, increased emphasis has been placed on water vapour levels within the compressed air stream. Though water vapour by itself is not a respiratory hazard, water vapour can condense at low ambient temperatures and during air expansion. Condensed water can adversely affect the operation of the breathing apparatus. Also, the presence of water vapour within the compressed air stream is a primary indicator that the purifier requires service since water vapour must be removed to prevent contamination of the activated carbon and catalyst beds. A properly designed cylinder refill system should include a moisture monitor as an integral component of the purification system to provide a warning of the need for service when desiccant beds are saturated.

Carbon Monoxide Monitor
OSHA 29CFR 29 1910.134 states the following in regard to compressed breathing air and carbon monoxide:

If an oil-lubricated compressor is used, it shall have a high temperature or carbon monoxide alarm, or both. If only a high temperature alarm is used, the air from the compressor shall be frequently tested for carbon monoxide to ensure that it meets specifications for human respiration.

A Carbon Monoxide (CO) Monitor is typically positioned downstream from the high pressure purification system. In the event of a high CO condition (10 ppm v/v or above per Grade E standards), the monitor should activate audible and visual alarms as well as shut down the compressor. The CO Monitor should include a means of calibration.


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