Exposure Limits for Carbon Monoxide from Various Government and Professional Organizations
There are several
goverment organizations and professional organizations that have posted
recommended exposure limits to Carbon Monoxide (mostly for the work
place). There is no single listing of all of these limits, and so we've
tried to summarize many of them on this page.
First, here are descriptions of some of the organizations that publish
these limits. Click on the logos to visit their official websites.
- Occupational Health
and Safety Administration (OSHA) - A Federal agency under the
Department of Labor that develops and enforces federal standards for
health and safety in the work place.
- National Institute
for Occupational Safety and Health (NIOSH)
- A Federal agency under the Department of Health and Human Services
that trains occupational health and safety professionals, conducts
research on health and safety concerns, and tests and certifies
respirators for workplace use.
- American Conference
of Governmental Industrial Hygenists (ACGIH) - An organization
of professional industrial hygiene personnel in government or
educational institutions. The ACGIH develops
and publishes recommended occupational
exposure limits each year called Threshold Limit Values (TLV's) for
hundreds of chemicals and physical agents.
Society of Heating, Refrigerating, and Air
Conditioning Engineers (ASHRAE) - An international trade
association that provides information
and sets standards for the
uniform testing and rating of heating, ventilation, air conditioning,
and refrigeration equipment.
Protection Agency (EPA) - A part of the US federal government
environmental laws and provides information and guidance to policy
Each organization has its own vocabulary to describe the
type of limit or level. Here is a summary of some commonly seen terms:
The table below summarizes some of the most up-to-date exposure
limits, including their date of publication.
- TWA - Time
Weighted Average. This is the level of CO (in PPM) that a person has
been exposed to on average over some period of time (usually 8 hours).
- PEL - Permissible
Exposure Limit. This is the term OSHA uses for the limits it publishes.
For CO, it happens that all of OSHA's PELs are actually TWA limits.
- Ceiling - An upper
limit on the concentration of CO at any moment. For example, a ceiling
value of 200ppm means that the level of CO should never rise above
- STEL - Short Term
Exposure Limit. This is a TWA defined over a short time period of 15
minutes. According to ACGIH, it should not be exceeded during any part
of a workday, even if the the 8-Hour TWA is within its limit.
- Excursion Limit -
An ACGIH term that refers to the Ceiling limit for a short period of
time (typically 15 - 30 minutes). This limit is used when no STEL is
published, and is defined as 5 times the 8-Hour TWA limit (Source:
ACGIH Handbook of TLVs and BEIs, 2004).
For more information on
Carbon Monoxide, and the health effects associated with different
concentrations, click here.