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Measurement of carbon dioxide, a byproduct of human respiration, is useful
in assessing the effectiveness of the mechanical ventilation system, which
supplies "fresh" outdoor air and exhausts stale indoor air. Elevated levels
of carbon dioxide, while harmless, indicate inadequate mechanical
ventilation.
Inadequate supply of outside air and/or inadequate exhaust of stale indoor
air have been associated with a variety of symptoms and illness, including
non-specific upper respiratory problems, headache, and fatigue. These
health problems are reversible with improvements in ventilation.
There are no federal, state, or local regulatory limits on carbon dioxide
that are applicable to indoor air quality issues. The American Society of
Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) recommends
that indoor levels not exceed outdoor levels by more than 700 parts per
million (ppm). Outdoor levels are usually 300-400 ppm.
CAUTION: Under normal circumstances, indoor air quality problems are often
resolved by increasing the supply of "fresh" outside air. In the current
uncertain circumstances, "fresh" outside air is not available. It is
therefore essential to adequately filter outside air with HEPA and
activated charcoal filters to protect against the possible intrusion of
potentially harmful contaminants.
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