Four Steps to Ensure Your Air is Clean

My simple current three-rule routine at all fill stations is as follows:

*Ask to see the compressor and its intake location. Assess for possible entrainment of vehicle or boat exhaust into intake. Assess risk for other contaminants in ambient air, such as the presence of paint or glue odors, or other industrial neighbors who could contaminate the intake. If there is a risk that cannot be quantified or assessed, then choose another operator.

*Test every tank for CO contamination prior to diving, with no exceptions. The one time you don't test is likely the time there will be CO contamination, which can and does come from the burning of an electric compressor's lubrication oil if overheated.

*Smell and taste the dive air in every tank prior to diving. There are hydrocarbon volatiles stored on the activated charcoal bed in the compressor's purifier, and if this bed is overheated, which is more likely in the tropics, a slug of narcotic hydrocarbons will be released from the charcoal bed back into the breathing air. Often these hydrocarbon contaminants can be detected by smell. Non-volatile oil mist can often be tasted in the breathing air.

* An optional step: Ask the fill station operator for the most recent air test. But in reality, these tests, even when done every three to six months, give a false sense of security. It's just better to assess the compressor intake for contaminant risk, and test every tank for carbon monoxide and odorous volatiles.