The US-based Scuba STAR Network is running the survey as the latest in its regular line of bi-monthly research into equipment and diving activity generally.
"Our July/Aug 09 Safety Survey is designed to explore the issues of air quality, including the types of fills that divers receive and the steps they take to verify air quality," says Scuba STAR.
The survey covers both standard air and oxygen-enriched air, nitrox.
Contamination can lead to serious problems for a diver. "Perhaps the most insidious contaminant is carbon monoxide," says Scuba STAR. "CO is a colourless, odourless gas that binds with the blood's haemoglobin and prevents oxygen from being carried.
"Exposure to CO even in very low concentrations can lead to serious injury and even death."
Contamination with CO, other gases or oil occurs usually due to "combustion of other contaminants during the compression process, which overwhelms the filtration process", "improper placement of the compressor inlet" or "improper maintenance of the compressor system".
In terms of checking the quality of fills, electronic or colour-change monitors are needed to assess any presence of CO or the mix ratios of nitrox. Simply sniffing the fill is a "crude gas quality test" which "won't detect CO" but will "sometimes detect odours caused by the combustion of oil or other contaminants".
Another error can be the incorrect labelling of cylinders' contents.
The most common problem, however, is water ingress. "While we might not consider water to be a physiological problem for the diver, it can take a toll on equipment and cause secondary contamination of the breathing gas," says Scuba STAR.
"Water can cause oxidation of the cylinder, and the formation of debris from the oxidation process can clog filters and foul regulators."
Scuba STAR aims to help recreational divers go about their sport in as safe a manner as possible - and to influence, where necessary, equipment manufacturers, trainers and others in a bid to improve diving products and techniques.
Its survey results are read with interest by industry insiders and, as such, carry influence with some of the industry's key decision-makers.
The online survey questionnaires can be completed in minutes. Respondents are assured of anonymity, and final reports are published on the websites of both Scuba STAR and DAN (Divers Alert Network).
To participate in the air quality survey, go to www.scubastarnet.com
Reports from previous surveys can be viewed at the site, and some appear on Divernet. Divers can also share their experiences on any safety-related subject by using the organisation's Anonymous Reporting Form.
Data is used in the compilation of Scuba STAR's Annual Safety Report.
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