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APPENDIX A: CO2 LEVELS AND GUIDELINES
1. CO2 Alarm Guidelines
The Occupational Safety & Health Administration (OSHA) requires by law that workers must be
protected from potentially dangerous high levels of CO2. There are 3 CO2 safety limits that must
all be followed:
•
5,000 ppm CO2
. This is the OSHA exposure limit for CO2 averaged over a 40 hour week.
•
5,000 ppm CO2 TWA
(Time-weighted Average). A workplace is considered unsafe if workers
are subjected to an average of 5,000 ppm CO2 or above for an 8-hour workday.
•
3% CO2 STEL
(Short Term Exposure Limit). At this CO2 level, an alarm must sound immediately,
and workers/occupants must leave the area.
for more details and to determine which alarm settings are best for your
application.
2. Indoor Air Quality
The Green/Yellow/Red LEDs are provided as a
quick check of indoor air quality (IAQ) in schools,
offices and similar buildings.
While there are several recommended standards,
the most commonly used is the American Society
of Heating, Refrigeration, and Air-Conditioning
Engineers (ASHRAE) standard, which states that
maximum indoor CO2 levels should be no more
than 700 ppm above outdoor CO2 levels. Since most outdoor CO2 is 400 ppm, this means that
1100 ppm is considered the maximum CO2 level for IAQ.
The National Institute for Occupational Safety and Health (NIOSH) considers indoor air
concentrations of carbon dioxide that exceed 1,000 ppm are a marker suggesting inadequate
ventilation.
In general, when measuring CO2 indoors, a green or yellow LED denotes acceptable IAQ. The red
LED suggests poor IAQ that should be corrected for the building occupant’s health and comfort.
