The "other" side

Kenelm Philip fnkwp at
Wed Aug 2 17:43:12 EDT 2000

> Indeed, it is well-established that outdoor air pollutants tend to
> accumulate at higher levels indoors than out.

That no doubt explains why the public health authorities in Fairbanks
warn children and elderly people to remain indoors when carbon monoxide
levels (in the winter), or forest fire smoke levels (in the summer) are

Seriously, it is an easily observed _fact_ that smoke levels are lower
indoors than outdoors. There is something called the 'penetration factor'
that is used when discussing the leakage of outdoor pollutants into
buildings. For most structures, this factor is small. The result, which
follows from applying some logic to the problem, is the following:

	For any _transient_ increase in outdoor pollutants (which is
certainly the case for anti-mosquito spraying), the indoor level will

1) peak at a lower level than outdoors
2) have a time-delayed peak compared to the outdoor peak
3) have a longer _duration_ indoors than outdoors

Item 3 comes from the fact that it will take some time for the indoor
pollutant to leak back outside after the outdoor paek has passed.

	Similar reasoning explains why, in cold climates, people's septic
tanks can freeze up in mid-summer. Temperature fluctuations in the air
penetrate into the ground in a time-delayed, reduced intensity manner.

	I am not trying to defend the anti-mosquito spraying in New York--
I agree with Gochfeld that it was ill-advised. But I find his statement
about indoor pollution from outdoor contamination very odd indeed. I
would like to see some evidence for his claim. Fairbanks recently had
very high levels of forest fire smoke--about 300 times above the EPA
recommended limits. When you walked into any building here you could
immediately detect, with your nose, the lower level of smoke.

						Ken Philip
fnkwp at

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