The use of personal safety equipment should always be seen as a last resort, only to
be adopted when all else has failed. With regard to exhaust gases, the practical
possibilities are limited, since all of the pollutants contained in the emissions are
difficult to filter out, which generally rules out the use of masks and the like.
Consequently, if the problem is to be solved using personal safety equipment, breathing
apparatus should be used. Such apparatus is inconvenient in practice because the oxygen
should come either from cylinders carried or worn on the back of the user or through a
hose.