This Safety and Health Information Bulletin is

not a standard or regulation, and it creates no

new legal obligations. The Bulletin is advisory in

nature, informational in content, and is intended

to assist employers in providing a safe and healthful workplace. The Occupational Safety and

Health Act requires employers to comply with

hazard-specific safety and health standards. In

addition, pursuant to Section 5(a)(1), the General Duty Clause of the Act, employers must

provide their employees with a workplace free

from recognized hazards likely to cause death or

serious physical harm. Employers can be cited

for violating the General Duty Clause if there is a

recognized hazard and they do not take reasonable steps to prevent or abate the hazard. However, failure to implement any recommendations

in this Safety and Health Information Bulletin is

not, in itself, a violation of the General Duty

Clause. Citations can only be based on standards,

regulations, and the General Duty Clause.

U. S. Department of Labor

Occupational Safety and Health Administration

Directorate of Science, Technology & Medicine

Office of Science and Technology Assessment

SHIB 04-27-2004

Safety and Health Information Bulletin

Introduction

The National Institute for Occupational Safety and

Health (NIOSH) and the Bureau of Labor

Statistics (BLS) have recently completed a national

survey of respirator use in the private sector.1 The

results of that survey are currently being analyzed

and prepared for publication. However, one

finding suggests that many employers may not be

exercising the proper care necessary to prevent a

type of fatal accident that can result from improper

use of air-line respirators. This Safety and Health

Information Bulletin is to alert the reader to

fatalities that have occurred due to the inadvertent

connection of air-line respirators to inert gas

supplies.

Background

Based on information obtained from Occupational

Safety and Health Administration (OSHA)

investigation reports from 1984 through 1995 and

more recently from the BLS, OSHA determined

that most worker fatalities involved regulatory and

procedural violations and could have been

prevented by proper training and compliance with

existing regulations.1,2,3 A number of the deaths

indicated that coupling compatibility problems and

lax supervisory oversight were major factors in the

inappropriate supply of non-respirable gas to the

respirators worn by these workers.

OSHA regulation (29 CFR 1910.134(i)(8)) and the

American National Standards Institute (ANSI)

standard Z88.2, “Practices for Respiratory

Protection,” specify that respirator air-line

couplings must be incompatible with outlets for

other gas systems to prevent inadvertent servicing

of air-line respirators with non-respirable gases or

oxygen.

Deaths Involving the Inadvertent Connection of Air-line

Respirators to Inert Gas Supplies
2

If an inert gas (e.g., helium, argon, nitrogen) is

inadvertently supplied to an air-line respirator

rather than breathable air, the results can be fatal.

Inert gases such as helium, argon, and nitrogen are

widely used in industrial settings as fire suppression

blankets for flammable work in confined spaces, to

operate pneumatic equipment, and to prevent

oxidation in industrial processes.

Air-line respirators are typically used in painting,

cleaning, some manufacturing operations, and

abrasive blasting. An air-line respirator, whether

configured with a hood, helmet, coverall, or

facepiece, must have a hose with terminal

detachable couplings. When a respirator’s air line

is connected to a source of inert gas rather than to

breathable air, the respirator wearer who trusts his/

her sense of breathlessness to determine whether

he/she is connected to breathing air has little

warning before losing consciousness.

This is because the buildup of carbon dioxide, not a

lack of oxygen, ordinarily causes the sensation of

breathlessness that may alert the individual wearing

the respirator. Consequently, the victim is fooled

because there is no clear indication that anything is

amiss. Blackout occurs quickly, without warning.

Victims wearing respirators connected to inert gas

lines are in a zero percent oxygen atmosphere, and

unconsciousness can occur in about 12 seconds2

and death in a matter of minutes. The situation

continues to be critical because victims are still

wearing respirators and continue to breathe inert

gas after they collapse.

Case Histories

Some case histories that appeared in the referenced

articles are presented below:

Case #1

An employee was using an air hammer to chip

residue out of a furnace at an aluminum foundry.

He was wearing an air-line respirator. Two

compressed gas lines with universal access

couplings were attached to a nearby post. The one

on the right was labeled “natural gas.” The gas line

on the left had a paper tag attached with the word

“air” handwritten on it; however, this line actually

contained pure nitrogen. A splitter diverted one

part of the gas stream to the air hammer and the

other part of the stream to the air-line respirator.

The employee was asphyxiated and killed when

exposed to pure nitrogen.

Case #2

A contractor crew was assigned to abrasively blast

inside a reactor vessel at a petrochemical refinery.

Although verbal company policy called for

contractors to supply all breathing air, this crew,

with supervisor’s knowledge, had on several

occasions used plant air to supply breathing air. A

crew member mistakenly hooked up his air-line

respirator to an unlabeled nitrogen line (only the

shut-off valve was labeled) used by the refinery for

purging confined spaces. Plant nitrogen and air

lines were identical, and both had couplings

compatible with the coupler on the respirator.

Case #3

An employee hooked the fresh air line of his

supplied-air respirator into a plant’s compressed air

lines and began abrasive blasting. The plant

operators, unaware that their plant air was being

used as breathing air, shut down the fresh air

compressor for routine, scheduled maintenance and

pumped nitrogen into the system to maintain

pressure and control the valves in the refinery. The

employee was overcome by the nitrogen in the air

lines and died of nitrogen asphyxia.

Case #4

An abrasive blaster at an air separation plant could

not obtain breathing air from an installed line. He

adapted unapproved hoses with quick-disconnect

couplers so he could connect an abrasive-blasting
3

respirator to a gas line supplying the blasting pot.

This piping was not color coded nor labeled in

accordance with company policy. The employee

died because he did not know he was connecting to

a nitrogen line instead of to compressed air.

Nitrogen was a separation by-product at this plant

and was piped to operate pneumatic equipment.

Case #5

A contract employee was abrasive blasting and

painting gratings and railings. The air-line from the

abrasive blasting respirator was hooked into the

plant air supply. The plant air supply was not

Grade D breathing air and was to be used only for

valve gauges and pneumatic tools. The air

compressor was shut down for maintenance, so

nitrogen was backfed into the plant air lines. No

one from the company informed the contract

employee that the lines now contained nitrogen.

When the abrasive blaster donned the abrasiveblasting respirator, he inhaled the nitrogen and was

asphyxiated.

Discussion

Individuals responsible for the use of air-line

respirators are urged to review their respiratory

protection programs to ensure that the couplings of

the respirator air lines are incompatible with any

other fittings used at the worksite. To ensure this

requirement is met, the non-respirator connections

must be changed. (The fittings of an air-line

respirator are tested and approved by NIOSH as

part of the unit. A user cannot make an

unapproved change to the respirator.)

Plant safety and health personnel should ensure

(determine) that nothing other than Grade D air

can enter the breathing air system. The NIOSH

approval label found on all air-line respirators

specifies that approval is valid only when supplied

with Grade D breathing air or equivalent. This is

also required by the OSHA respiratory standard

and the ANSI Z88.2 standard.

There must be a concerted engineering effort to

design and maintain separate gas distribution

systems for breathable air, and for pneumatic tools,

fire suppression, and other work-related needs, so

that improper gas interconnections cannot be

made. Implementing color coding and labeling for

all gas lines is a good safety practice that should be

followed to ensure that mix-ups do not occur.

Quick Connectors

The diagram in Figure 1 shows the proper method

of coupling sections of air supply hose using

locking quick disconnects, which are easily

connected by pushing the plug and socket together.

To separate, the plug and socket must be pushed

Figure 1. Quick Connector Diagram

Quick connectors allow the supply hoses to be connected to specific gas connection points. Insertion

into an incorrect outlet is prevented by the use of different shapes for mating portions, different spacing

of mating portions, or some combination of these.
4

together and the sleeve on the socket retracted

from the plug.

Conclusion

To help ensure that workers do not inadvertently

hook up to inert gas supplies, the following

recommendations should be implemented:

• Ensure that all requirements related to

respiratory protection as outlined in

29 CFR 1910.134 are met. Written

standard operating procedures governing

the selection and use of respirators must be

developed and implemented. Requirements

for training and instruction in the proper

use of respirators and their limitations must

be met at all facilities.

• Ensure (determine) that the couplings of

the respirator air lines are incompatible

with any other couplings/fittings for nonrespirable air or gas delivery systems.

Replace couplings on non-breathing air

systems with another, incompatible type of

coupling.

• Ensure that breathable air systems are not

in any way interconnected to nonbreathable air systems.

• Develop a maintenance procedure to

address supply-line identification (labeling)

and painting. Stress the purpose of color

coding and the importance of completing

detail painting in a timely fashion to ensure

that this visual cue is always available to aid

workers.

References

1. U.S. Department of Labor, Bureau of Labor

Statistics, and the U.S. Department of Health

& Human Services, National Institute for

Occupational Safety and Health, Centers for

Disease Control and Prevention (CDC).

Survey of Respirator Use and Practices,

2000.

2. Hudnall, J.B.; Suruda, A.; and Campbell,

D.L. Deaths Involving Air-Line Respirators

Connected to Inert Gas Sources. American

Hygiene Association 54(1): 32-35 (1993).

3. Suruda, A.; Milligan, W.; Stephenson, D.; and

Sesek, R. Fatal Injuries Involving

Respirators, 1984-1985. Applied

Occupational and Environmental Hygiene

18(4): 289-292, 2003.