Got this from Newport Diving Center Thames st.
To get Carbon Monoxide you have to have a compressor that runs on fuel OR the intake must be where there is allot of car traffic, I know that The Newport Diving Center and Fire Ex run Electrical compressors and their intakes are no where near where any cars would be. Also if there was a problem I am sure the shop would have been visited immediately by the state of Rhode Island to check the air and/or shut down there air fill station until the problem was resolved, I know my store has not been visited, I do not know about Fire Ex, but sure they has not been visited either. Find it amazing only 3 divers and not allot more got this as stores fill allot of tanks - our store over 300 in the last 2 weeks, I honestly think there is something fishy here.
Right from the Encyclopedia Britannica:
carbon monoxide, (CO), a highly toxic, colourless, odourless, flammable gas, it is also present in the exhaust gases of internal-combustion engines and furnaces as a result of incomplete conversion of carbon or carbon-containing fuels to carbon dioxide.
So as stated above I know the Newport Diving Center and Fire Ex run Electrical Compressors and there intakes are no where near Vehicle Traffic