Can a Humidity Differential move PM2.5 Pollution? Observations

There is a higher level of PM2.5 pollution outside of the house. Readings are in the 80-150 range due to wildfires. (PM2.5 levels determined by sensors in PurpleAir.com's sensor network)
Using a handheld air monitor that can measure PM2.5 readings were taken indoors.
Most rooms in the house are reading +/- 40, but one room read 450
smokey haze could be seen in the room during the highest readings (what alerted us to the problem)
relative humidity outside is typically low (30-40%)
the room with the high reading (450 PM2.5) has

high humidity (80-90%) to support tropical plants
windows from the 1990s (older, don't seal well)
an attic access panel that allows some air movement
no fans that would draw in air from outside or push air outside
room is long and skinny (40'x15') with windows along the long axis and has a door halfway down the 40' axis
one end has higher humidity (where the humidifier is)


putting 3 small HEPA filters in the room can reduce PM2.5 to 5 in about an hour. After about 10 hours, readings of PM2.5 are much higher 80-400
if we reduce the PM2.5 to under 10 and close the door halfway along the 40' axis of the room, the lower humidity side of the door stays free of PM2.5 whereas the PM2.5 on the higher humidity side of the door continues to increase.
there is no internal source of PM2.5 - this only started this week as smoke has blown into the area

Q: what's the likelihood that the humidity differential between indoors and outdoors is &quot;pumping&quot; air and effectively pulling smoke indoors?
Q. What's the likelihood of the humidity differential being able to concentrate the smoke indoors (there have been no readings outside that come close to the 450 PM2.5 that was seen indoors, could the humidity differential be &quot;pumping&quot; pollution indoors and concentrating it)?
Q. what else might be contributing or causing this?
Humidity or recent rain plays a huge difference in air pollution. Seattle has less air pollution, because the effect of heavy rain and water accumulating on particles 'wash&quot; the air. In hotter, drier Los Angeles the pollution stays in the air longer because there's less moisture to weigh it down. Mold, spores, dust and allergens do thrive in humidity but those aren't Pollutants in the classical industrial sense.