Hi,

That is a very good question, safety of the works is of course the most important!

You are right with your concerns. The compressor will suck in anything that is present in the outside air, including exhaust smoke, dust and Carbon monoxide (CO). It will just compress anything that is present in the outside air and pump it to the confined space.

So yes, if the compressor sucks in exhaust fumes, it can be a danger for the workers in the confined space. Especially, because exhaust gas contains Carbon monoxide (CO), which is colorless and oderless but very toxic to humans.

Also, since it is a portable compressor, I assume it is a oil injected rotary screw compressor, right not (oil-free type). Or is it a small oil-free piston compressor?

All oil flood screw compressors have the problem of oil carry-over: a small part of the oil leaves the compressor together with the compressed air. So we need to take care of that too..

Yes, you can use the portable air compressor for breathing air, BUT you need to clean the compressed air before it's good enough for breathing air.

USA and Canada describe breathing quality air as follows, I guess in your country it would be about the same levels:

Contaminant: USA / Canada Carbon Monoxide (ppm v/v): 10 / 5 Carbon Dioxide: 1000 / 500 Oil (Condensed Hydrocarbons) mg/m3: 5 / 1 Odor: "lack of noticeable odor" / "free of any detectable odor" Dew Point: As Required / -40°F (-40°C)

So, we basically need to: remove dust, remove Carbon dioxide and monoxide and odors from the compressed air.

There are special filters available to do the job for you. Install them after the air compressor.

For filtering the air, I would suggest the following:

1. Pre filter: removes general dust, and large particles.

2. coalescing filter: removes all small water and oil drops and mist in the compressed air + removes remaining dust.

(* We now have clean compressed air, without any water, oil or dust. But, we still have CO, CO2 (if engine exhaust is sucked in) and smells *)

To remove CO, we need a special type of filter, called a hopcalite catalyst filter. This transforms the CO to the harmless CO2. But, to use this special filter, the compressed air must first be dried with a compressed air dryer, otherwise it doesn't work..

3. Air dryer. Dewpoint -40 degrees Celsius

4. Hopcalite catalyst filter. Transforms CO to CO2

5. Activated carbon filter. Removes smells/odors.

So, quite a long list... If you can make sure that no CO / exhaust fumes is sucked in, you can get away with only 1, 2 and 5. Those filters are very common and not too expensive. The workers should wear a portable CO / Oxygen detector to be safe (but I think they already have that).

Also, always check with your local rules and laws. (I tried my best to give the best and correct information, but I cannot be held responsible for damage or injuries).

Here are some links which might be useful:

http://www.factair.co.uk/breathing-air/safe-air-cabinets-and-trolleys/ - Filter trolleys, for use with breathing masks, with and without CO filter option. Contact them for more advice.

And here are some big breathing are filters. You can install these right behind your compressor.

http://www.compressorworld.com/135-CFM-Deltech-Del-Monox-DM-Series-Breathing-Air-p/dm135.htm

http://www.spx.com/en/deltech/pd-del-monox-breathing-air-systems/

http://www.airceldryers.com/products/breathing-air-system/

Alright, long story, but I hope it was of any help. If you got more questions, just let me know.

Good luck!