Originally Posted by
BobL
"Play" might be the operative word here.
I use 4 particle counters (that can actually measure dust levels even when it can't be seen) including access to two pro level counters that I access from my place of former employment. I have been using the pro instruments since 1978.
You simply cannot tell by looking at at any dust especially smoke when you think its all gone there is still a lot of small stuff around.
During the last few months in Perth there have been several smoke alerts from prescribed burnoffs and I have monitored their progress with my particle counters.
The detectors can detect smoke well before it can be smelled and seen. This showed me that judgments based on anything that can be seen are a waste of time.
RE: 20 room changes per hour emptying a room in 3 minutes
It just doesn't work like that. Ventilation works at best on a half emptying principle.
The first room change removes AT BEST half the dust in the room, Assuming NO MORE DUST has been added, the next room change empties another half of the remaining dust, and the next room change removes another half etc.
So the sequence goes 1/2, 1/4, 1.8, 1/16, etc
20 room changes per hour is at best andin practice about 10 room changes per hour and remember that assumes that no more dust is generated during this time.
20 room changes per hour is actually less than desirable but it works for small sheds but the "Fannage" required for large DIY sheds become impractical because of things like the noise and power requirements. There are quiet low powered high volume fans out there that use squirrel cages but these cost $$.