Many
gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
es have
toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
properties, which are often assessed using the
LC50 (median lethal dose) measure. In the United States, many of these gases have been assigned an
NFPA 704
"NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response" is a standard maintained by the U.S.-based National Fire Protection Association. First "tentatively adopted as a guide" in 1960, and revised sev ...
health rating of 4 (may be fatal) or 3 (may cause serious or permanent injury), and/or exposure limits (
TLV,
TWA
Trans World Airlines (TWA) was a major American airline which operated from 1930 until 2001. It was formed as Transcontinental & Western Air to operate a route from New York City to Los Angeles via St. Louis, Kansas City, and other stops, with ...
or
STEL) determined by the
ACGIH
The American Conference of Governmental Industrial Hygienists (ACGIH) is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio. One of its goals is to advance worker p ...
professional association. Some, but by no means all, toxic gases are detectable by
odor
An odor (American English) or odour (English in the Commonwealth of Nations, Commonwealth English; American and British English spelling differences#-our, -or, see spelling differences) is caused by one or more volatilized chemical compounds ...
, which can serve as a warning. Among the best known toxic gases are
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
,
chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
,
nitrogen dioxide
Nitrogen dioxide is a chemical compound with the formula . It is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year for use primarily in the producti ...
and
phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
.
Definition
*Toxic: it is a chemical that has a median lethal concentration (LC
50) in air of more than 200
parts per million
In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they ...
(ppm) but not more than 2,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 20 milligrams per liter of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.
*Highly Toxic: a gas that has a LC
50 in air of 200 ppm or less.
*
NFPA 704
"NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response" is a standard maintained by the U.S.-based National Fire Protection Association. First "tentatively adopted as a guide" in 1960, and revised sev ...
: Materials that, under emergency conditions, can cause serious or permanent injury are given a Health Hazard rating of 3. Their acute inhalation toxicity corresponds to those vapors or gases having LC
50 values greater than 1,000 ppm but less than or equal to 3,000 ppm. Materials that, under emergency conditions, can be lethal are given a Health Hazard rating of 4. Their acute inhalation toxicity corresponds to those vapors or gases having LC
50 values less than or equal to 1,000 ppm.
List
Notes
# Decomposes in gaseous form.
# Explodes in gaseous form.
See also
*
List of Schedule 1 substances (CWC)
Schedule 1 substances, in the sense of the Chemical Weapons Convention, are chemicals which can either be used as chemical weapons themselves or used in the manufacture of chemical weapons and which have no, or very limited, uses outside of chemic ...
*
List of extremely hazardous substances
This is the list of extremely hazardous substances defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002). The list can be found as an appendix to 40 C.F.R. 355. Updates as of 2006 can be seen on ...
*
List of gases
This is a list of gases at standard conditions, which means substances that boil or sublime at or below 25 °C (77 °F) and 1 atm pressure and are reasonably stable.
List
This list is sorted by boiling point of gases in ascending ...
References
{{reflist
External links
OSHA Limits for Air ContaminantsOSHA Permissible Exposure Limits
Chemical safety
Highly toxic gases
G