BRIAN DUNAWAY, LEW ROCKWELL SITE - Houston press has reported that
Lowe's and Home Depot stores throughout Harris County have sold out of
the plastic sheeting, duct tape, and other supplies recommended by the
Office of Homeland Defense in order for citizens to be better prepared
in the event of an terrorist act. It's the same all over the nation. . .
The cause for most concern is the OHD plan for "What to do during a
chemical or biological attack" - Seek shelter in an internal room,
preferably one without windows. Seal the room with duct tape and plastic
sheeting. Ten square feet of floor space per person will provide
sufficient air to prevent carbon dioxide build-up for up to five hours.
Good Morning America's Home Improvement Editor, Ron Hazelton, assured
his viewers:
"Don't worry about running out of air. Every ten square feet of floor
space will last an adult about 5 hours. And don't leave the room until
you get instructions from the Emergency Broadcast System to do so."
Hazelton is actually correct (probably accidentally) that the amount of
oxygen corresponding to a ten square foot space is probably sufficient
(though marginal) to sustain an adult for about five hours, but the
critical issue is not oxygen consumption, but carbon dioxide generation
and accumulation. The OHD statement is correct in identifying carbon
dioxide accumulation as a concern, but its conclusions are surprising,
to say the least. Assuming an eight-foot ceiling (yielding eighty cubic
feet per person) and a subject metabolic rate of 800 BTU/hr, after five
hours the partial pressure of carbon dioxide (ppCO2) would be ~67 mm Hg
(if the initial ppCO2 were zero). It cannot be understated: this is very
high.
(Note: 800 BTU/hr (3.36 kcal/min) is not unreasonable for a very excited
person in a hot and humid enclosure with elevated carbon dioxide (more
on that in a moment). For this case, a bare (but irresponsible) minimum
might be 600 BTU/hr (corresponding to a ppCO2 level of 50 mm Hg after
five hours). Consider that NASA Environmental Control and Life Support
(ECLS) engineers typically assume a waking metabolic rate of 450 BTU/hr
for moderate intravehicular activity, and this is with very physically
efficient subjects (astronauts) not using major muscle groups (e.g.,
legs) in microgravity.)
Keep in mind that the maximum operational limit for the Shuttle Orbiter
is 7.6 mm Hg, and is actually lower for the International Space Station.
The NASA Spacecraft Maximum Allowable Concentration (SMAC) for carbon
dioxide is 10.0 mm Hg for a one-hour period. Similar values can be found
among the literature of the various military branches.
The NASA Bioastronautics Data Book (Second Edition, pp. 48-49) indicates
that after only 80 minutes, at a ppCO2 level of ~18 mm Hg, the subject
can experience "mental depression, headache, dizziness, nausea." At ~45
mm Hg (after 80 minutes), the subject experiences "marked deterioration
leading to dizziness and stupor, with inability to take steps for self
preservation. The final state is unconsciousness." (The level in our
case would not reach 45 mm Hg after 80 minutes, but the threshold of the
aforementioned symptoms would be at a much lower CO2 level at the end of
five hours.)
Industry literature is similar.
The W.E. Kuriger Associates web page titled "Carbon Dioxide Fact Book,"
states that,
Several studies have indicated that CO2 does not seriously impact human
health until levels reach approximately 15,000 ppm [7.5 mm Hg]. ... At
extremely high levels, i.e., 30,000 ppm [15 mm Hg] (these concentrations
are usually never reached in a standard home), the symptoms can include
nausea, dizziness, mental depression, shaking, visual disturbances and
vomiting. At extremely high levels, loss of consciousness may occur. . .
Finally, CO2 is an asphyxiate, a condition in which an extreme decrease
in the amount of oxygen in the body, accompanied by an increase of
carbon dioxide, leads to loss of consciousness or death. Concentrations
of 100,000 ppm [50 mm Hg] or more of CO2 can produce unconsciousness or
death.
And carbon dioxide is hardly the only physiological concern.
One would probably pass out from heat exhaustion before he passed out
from exposure to high carbon dioxide concentrations.