At the PPM required for cognitive impairment, how long does someone need to be in the area for this to measurably affect them? I know at my workplace, we tend

At the PPM required for cognitive impairment, how long does someone need to be in the area for this to measurably affect them? I know at my workplace, we tend to have short meetings (thankfully!). However we inhabit the upper sections of old downtown square, which was 7 different buildings architecturally "glued" together. But when we do have meetings, they're back to back with other meetings given the shared meeting space. But this is even more sinister if what I'm thinking is correct: the toxins accumulate even if it doesn't impair the first meeting (or 3), and effects worsen through the day for anyone in there.