Isn't that quite explosive there with all the Methane in the air ?
It is still by far not that high concentration.
In the garbage incineration facility here the air for the combustion is drawn from the stinking storage pit (well, in fact the biggest "room" in that building). The reason is mainly to keep some negative pressure there (so the smell won't go out) and to destroy the smelly gasses in the hot flames. With this, any really dangerous buildup is prevented (there are more prominent evil gasses than methane - e.g. H2S,...). But this flow is not enough to remove the smell from the room. The operator cockpits (crane,...) are then filled by fresh air from the outside, so maintain positive pressure towards the room itself, so keep the working environment reasonable there. But of course, if someone has to manually sort something out really in the main room itself, the only thing he has is his PPE (so a simple filter mask). Bu that kind of tasks are rather exceptional and of rather short duration (fortunately for them; it is usually to fix or unblock something or so, so no longer than few minutes).
