NitrogenEnriched

Atmospheres

Can Kill!

For additional information or to view the entire

Safety Bulletin, please contact:

U.S. Chemical Safety and

Hazard Investigation Board

2175 K Street NW, Suite 400

Washington, DC 20037-1848

202-261-7600

www.chemsafety.gov

U.S. Chemical Safety and Hazard Investigation Board

The U.S. Chemical Safety and Hazard Investigation

Board has published a Safety Bulletin on nitrogen

asphyxiation. This brochure summarizes that

material.

Data sources for the CSB review of nitrogen

asphyxiation incidents include regulatory agencies,

media reports, technical publications, and contacts

with safety personnel; however, only those incidents that were reported and accessible are

evaluated. Although the summary data are not allinclusive, the numbers clearly indicate that nitrogen

asphyxiation presents a serious hazard in the

workplace.1

1 Statistical analysis is based on available, limited information.

2003-10-B June 2003
N

ITROGEN makes up 78 percent of the air we breathe. It is a colorless, odorless gas that is safe only when

mixed with an appropriate amount of oxygen. These two gases cannot be detected by the sense of smell.

A nitrogen-enriched environment, which depletes oxygen, can be detected only with special instruments.

Oxygen deficiency has a range of effects and can be fatal if concentrations fall below 10 percent.

Facts About

Nitrogen Asphyxiation

Eighty-five nitrogen asphyxiation incidents

from 1992 to 2002 resulted in 80 deaths

and 50 injuries.

The majority of incidents occurred in

manufacturing and industrial facilities, but

other settings included laboratories and

medical facilities.

Most incidents occurred in and around

confined spaces, though several incidents

occurred in “open” areas, including inside

buildings and outside in the vicinity of

equipment.

Almost half of the incidents involved

contractors, including construction workers.

Among the causes of death and injury were

failure to detect an oxygen-deficient

atmosphere in and around confined spaces,

using nitrogen instead of breathing air, and

inadequately preparing for rescue.

o Implement warning systems and

continuously monitor enclosures and areas

where additional amounts of nitrogen can be

expected to enter, recognizing that the

atmosphere may change over time.

o Ventilate with fresh air before and during

work in areas that could contain elevated levels of

nitrogen.

o Implement a system for confined space

entry and safe rescue of workers, including

having personnel wear a harness and lifeline

attached to a mechanical retrieval system, having

standby personnel available at all times to

communicate with personnel inside confined

spaces, and ensuring that rescuers are properly

trained and equipped.

o Ensure the uninterrupted flow and

integrity of breathing air by verifying the

oxygen concentration of supply air, routinely

inspecting air supply equipment such as hoses

and compressors, and continually monitoring the

air supply system for contaminants.

o Prevent the inadvertent mix-up of

nitrogen and breathing air by ensuring that

incompatible fittings and clear labels are in place

on cylinders, piping systems, and supply lines.

o Develop and implement a comprehensive

training program that covers proper use of

ventilation systems, safe practices for confined

space entry and rescue, unique connections and

fittings on cylinders containing different gases,

and proper use of air supply equipment.

Good Practices

Prevent Nitrogen Asphyxiation

Nitrogen is widely used commercially to keep material free of contaminants, including oxygen—

which can corrode equipment or present a fire and explosion hazard when in contact with flammable liquids or combustible solids. Good practices must be followed to prevent nitrogen asphyxiation, as highlighted below.