Delta_P
Contributor
It shouldn't happen ever. As pointed out above, it happens when someone doesn't drain the water separator (filter) on the compressor at least every 15 minutes. If you're seeing water in the output the filter system is saturated and not working - you might as well remove the filter cartridges and breathe straight from the compressor for all the good they're doing.
This could be a teachable moment for the shops if you're up to it.
1) Ask each shop if their compressor has an autodrain. The autodrain is basically a series of electrically operated drain valves hooked to a timer. If the shop's compressor does have an autodrain then the source of your water/oil is far more likely to be a shop that relies on their compressor operator not being distracted by clients in the front while tanks are filling.
It is possible that an autodrain might be faulty, and the shop needs to know this.
Even with an autodrain the filters can saturate if too much air is pumped through them. Human error again, but it takes longer to catch up with us. Filters need to be changed after they've processed a certain volume of gas.
2) Ask if the shop has a moisture detector on their filter system. On smaller stationary systems this is usually an eyeball port on the top of the final filter vessel, or a small cylinder plumbed into the output line like #14 on this page: Max-Air | paintball air, paintball compressor, SCUBA recharge air or this widget: Colorimetric Air Quality Monitor
There will be a disk visible through this port. Often this is a golden brown disk surrounded by a blue ring. The centre disk is CO; any trace of black is a valid excuse to run from the shop screaming. The outer ring is the moisture detector. It should be blue. Pink, and you've found your problem. Same principle with the multi-sector moisture only detector shown in the GMC link.
Filters might have their own moisture detector strip built into the side of the cartridge. Unfortunately you have to actually open the filter vessel and pull the cartridge in order to check it.
3) I agree about asking to see an air test certificate, however usually the only thing the certificate shows is that the compressor was producing clean air immediately after the last filter change. (If you find a shop that pulls samples before changing the filters buy them a beer and give them your business.) More useful information is that if the shop has "misplaced" the air tests they probably aren't following other maintenance and operating procedures properly either.
The only law I know of requiring regular air tests for sport diving compressors is in Florida. Maybe Quebec if I knew French well enough to decipher the regulations.
You need to get the tanks and valves cleaned thoroughly. It is possible to breathe condensate contaminated tanks without getting lipoid pneumonia (don't ask me how I know) but you don't want to risk it.
