U.S. Department of Labor t www.osha.gov t (800) 321-OSHA (6742)

Fact Sheet

Shipyard

Employment

Hazards during the Repair and 

Maintenance of Refrigeration 

Systems on Vessels

The repair and maintenance of refrigeration systems can present hazards to both workers servicing these 

systems and those in the general area. The two main types of hazardous refrigerants used in vessel 

refrigeration systems are ammonia and halocarbons (the most commonly recognized is Freon®). The 

latter include chloroflourocarbons (CFCs), hydroflourocarbons (HFCs), and hydrochloroflourocarbons 

(HCFCs), such as chlorodifluoromethane (R-22) or difluoromonochloromethane (R-134A). Worker exposure 

to these compounds may occur during maintenance and repair activities, or as a result of leaks. Depending 

on which refrigerant is used, different precautions may be required. 

Ammonia

Ammonia, in liquid or gas form, can present hazards to workers’ skin, 

eyes, nose, and lungs. Liquid ammonia is a clear fluid that evaporates 

quickly at room temperature. As a gas, ammonia is colorless and 

has a strong odor that is suffocating, pungent, and penetrating. It is 

much lighter than air, so if ammonia gas escapes from a refrigeration 

system or a storage container, it may collect in high areas or ceilings. 

Liquid releases can form aerosols that may tend to accumulate at 

low points. Therefore, it is important to take atmospheric readings 

at various locations within a space to ensure that it is safe for workers. 

While ammonia has a low odor threshold (as low as 2 ppm), which 

makes it easy to detect even in low concentrations, workers who 

have been exposed to ammonia regularly (or repeatedly) may 

experience a significant reduction in their ability to detect ammonia 

by smell. Exposure to ammonia at 300 ppm is immediately 

dangerous to life and health. Where there is a potential for 

overexposure to ammonia, employers must provide workers with 

proper safety equipment and ensure its use (29 CFR 1915.152(b)). 

Personal protective equipment (PPE) should be used when there is 

a possibility of exposure above 50 ppm. See 29 CFR 1915.154 (29 

CFR 1910.134) for detailed information on proper respiratory 

protection. Ammonia is flammable at all concentrations and 

explosive between 15% and 28% (150,000 - 280,000 ppm) in air. 

If ammonia is released in an enclosed space with an ignition 

source, an explosion may occur.

Photos: Amy Sly, Sound Testing, Inc.

Examples of refrigeration systems aboard vessels.
U.S. Department of Labor t www.osha.gov t (800) 321-OSHA (6742)

Employers with systems containing 10,000 pounds or more of 

ammonia must follow the requirements in 29 CFR 1910.119

(Process Safety Management of Highly Hazardous Chemicals) for 

controlling hazards associated with a release of ammonia. 

Employers must: 1

• Identify hazards through a process hazard analysis and ensure 

that they are controlled to protect workers (29 CFR 1910.119(e)). 

The hazard analysis must be revalidated at least every five years 

(29 CFR 1910.119(e)(6)).

• Develop and implement written operating procedures for workers 

on vessels to follow based on the results of a detailed hazard 

analysis (29 CFR 1910.119(f)(1)). OSHA requires that these 

procedures be reviewed as often as necessary and certified as 

current and accurate at least annually (29 CFR 1910.119(f)(3)). 

• Verify that refrigeration equipment complies with good 

engineering practices and that it is operated in a safe manner 

(29 CFR 1910.119(d)(3)(ii), (iii)). 

• Train maritime workers on the safety and health hazards 

associated with using ammonia, on emergency operations 

(including shutdown), and on safe work practices that apply to 

their job tasks (29 CFR 1910.119(g)(1)(i)).

• Check on each worker who works alone at regular intervals by sight 

or verbal communication, including at the end of the job assignment 

or workshift, whichever occurs first (29 CFR 1915.84).

Common Exposure Thresholds for Ammonia

Range Hazards

2–55 ppm Normal range of odor threshold

Note: If the smell of ammonia is detected and/

or you experience eye irritation, leave the area 

immediately and notify the appropriate person.

70 ppm Tingling or burning in eyes, nose, or throat; can 

cause watering of eyes, sneezing, and coughing

300 ppm Severe irritation of eyes, nose, or respiratory 

tract, which becomes intolerable after a few 

minutes; difficulty breathing; possible burning in 

lungs (IDLH level)

2,000 ppm 

or more

Can be fatal after a few breaths

1

 The Process Safety Management standard has 14 enforceable elements. This summary 

highlights certain key requirements of 29 CFR 1910.119, but employers covered by the 

standard must comply with all 14.

For additional information on worker safety when 

exposed to ammonia see: 

• OSHA Safety and Health Topics Page – 

Ammonia Refrigeration

• OSHA eTool - Ammonia Refrigeration

Halocarbons 

The use of certain halocarbons (CFCs and HCFCs) is being 

phased out in the United States, although it is expected that these 

refrigerants will not be fully removed from use until around 2030. 

In addition to trying to use alternative refrigerants that are safer for 

workers and the environment, employers still must assess work 

activities to determine if such hazards are present, or are likely to 

be present (29 CFR 1915.152(b)). Where a workplace assessment 

determines that using PPE is necessary, the employer must equip 

affected workers with the type of PPE that will protect them from 

the identified hazard(s) and explain its selection in a manner that 

each worker understands (29 CFR 1915.152(b)(1) and (2)).

Halocarbons, which exist both as a liquid or gas, are not easily 

ignited and do not burn rapidly if ignited. Halocarbons are heavier 

than air, which can lead to asphyxiation in a confined space due to 

the displacement of oxygen. As a liquid, many of these colorless 

compounds are volatile and give off vapors with a faint sweet odor. 

Overexposure to halocarbons can cause dizziness due to the lack 

of oxygen, which is a warning sign of the onset of asphyxiation. At 

higher exposure levels and with long periods of worker exposure, 

central nervous system depression, cardiac arrhythmia, and death 

may result.

When performing hot work in the presence of halocarbons, 

decomposition products such as hydrochloric acid (HCI), 

hydrofluoric acid (HF) and carbonyl halides may form. These 

compounds can be toxic at very low concentrations. All hot work 

should be stopped during any halocarbon refrigerant leak to 

prevent worker exposure to such toxic compounds, as well as the 

risk of fire or explosion.

Numerous halocarbon refrigerants are used in cooling systems 

and new, more environmentally friendly compounds are constantly 

being developed. Many of the newer halocarbon refrigerant 

replacements do not have Permissible Exposure Limits (PELs). 

Depending on the refrigerant used, employers should consult the 

PELs listed in 29 CFR 1915, Subpart Z, or the manufacturer’s 

Safety Data Sheet (SDS). Some common halocarbons used 

as refrigerants include dichlorodifluoromethane (R-12), 

dichlorotetrafluoroethane (R-114), and trichlorofluoromethane 

(Freon 113). These specific compounds are assigned a PEL of 

1,000 ppm. Refer to their common exposure thresholds below. 
U.S. Department of Labor t www.osha.gov t (800) 321-OSHA (6742)

Common Exposure Thresholds for Halocarbons 

(R-12, R-114, and Freon 113)

Range Hazards

1,000 ppm Normal range of odor threshold

75,000–100,000 ppm Agitation and dizziness

200,000 ppm Drowsiness, or unconsciousness

300,000 ppm or more Can be fatal after just a few breaths

Safety Requirements and Recommended 

Best Practices for Ammonia- and 

Halocarbon-Based Systems

• Employers must provide and ensure that workers use 

appropriate protective equipment (such as impervious clothing, 

gloves, splash-proof safety goggles, face shields - eight-inch 

minimum) to prevent repeated or prolonged skin contact with 

liquid refrigerants (29 CFR 1915.152(a)).

• Employers must provide and ensure that workers wear 

appropriate respiratory protection determined to be necessary 

by a workplace hazard analysis (29 CFR 1915.152(b) and 

1915.154 (see 29 CFR 1910.134). Where atmospheric 

conditions are immediately dangerous to life or health (IDLH), 

such as during a leak, employers must provide workers with 

appropriately protective supplied-air respirators or escape-only 

respirators that meet the requirements of 29 CFR 1910.134(d)

(2). Air-purifying respirators, which would not adequately protect 

workers in IDLH atmospheres, may not be used. 

• When workers’ responsibilities include responding to a possible 

refrigerant leak, employers must have a written emergency 

response plan in place (29 CFR 1910.120(q)(1)). The plan 

must include an explanation of worker personnel roles, lines of 

authority (including designation of a “senior official”), necessary 

training, communication protocols, and PPE (see 29 CFR 

1910.120 (q)(2)(i) through (q)(2)(xii), and (q)(3)(i)).

• Note: All ignition sources must be secured and effective 

ventilation installed to rid the area of refrigerant vapors (29 CFR 

1915.12(b)(2)). Unprotected personnel may not return to the 

affected area, especially bilge areas, until the atmosphere has 

been tested and the space is determined to be safe (29 CFR 

1915.12(b)(3)).

• Verify atmospheric safety, using a detector tube or other 

appropriate instrument, to ensure that no dangerous level of 

halocarbon or ammonia is present (29 CFR 1915.12(b)). 

• In the event that a refrigerant leak occurs and there is no 

immediate way to identify or reasonably estimate worker 

exposure to the potential respiratory hazard, employers must 

consider the atmosphere to be IDLH and initiate the appropriate 

emergency procedures necessary (29 CFR 1910.134(d)(1)(iii)). 

• Use mechanical ventilation to bring concentrations of airborne 

refrigerants within the Permissible Exposure Limit (PEL)/

Recommended Exposure Limit (REL) (29 CFR 1915.12). If 

concentrations are still above an acceptable level, proper 

respiratory protection must be provided (29 CFR 1915.154 

(see 29 CFR 1910.134)). 

• Ensure that all refrigerant, including vapor, is removed and that 

the pressure is at 0 psig before disassembling a refrigeration 

system.

• Before hot work is performed on refrigerant lines, they should 

first be purged using inert gas to reduce combustion and toxicity 

hazards. The work area must then be tested and certified by 

a Marine Chemist or a U.S. Coast Guard-authorized person as 

“Safe for Hot Work” (29 CFR 1915.14(a)(1)).

• When repairs are completed, retest the lines to determine if the 

leak was successfully repaired. If the repairs do not stop the 

leak, shut down the unit until it can be properly repaired.

• When refrigerants are stored in compressed gas cylinders, 

workers should handle them with extreme caution, as there is 

the potential for frostbite due to escaping liquid refrigerant. If 

liquid refrigerant comes into contact with a worker’s skin, wash 

the exposed area immediately with water and treat the skin for 

frostbite. Liquid leaks can produce extremely large volumes of 

vapor upon release, presenting toxicity and/or fire and explosion 

hazards.

• Refrigerants kept in pressure vessels, drums or containers 

must be stored a safe distance from an open flame, hot metal, 

or other sources of artificial heat that may lead to an explosion 

(29 CFR 1915.173(c)).

• Evaluate the location and interaction of refrigeration systems 

with other equipment to identify potential hazards such as fire 

or explosion (29 CFR 1910.120(c)(7)). For example, there is a 

greater potential for an ignition source to be located in a main 

propulsion room than in an auxiliary machine space.

Workers’ Rights

Workers have the right to:

• Working conditions that do not pose a risk of serious harm. 

• Receive information and training (in a language and vocabulary the 

worker understands) about workplace hazards, methods to prevent 

them, and the OSHA standards that apply to their workplace. 

• Review records of work-related injuries and illnesses. 
U.S. Department of Labor t www.osha.gov t (800) 321-OSHA (6742)

• File a complaint asking OSHA to inspect their workplace if they 

believe there is a serious hazard or that their employer is not 

following OSHA’s rules. OSHA will keep all identities confidential.

• Exercise their rights under the law without retaliation, including 

reporting an injury or raising health and safety concerns with their 

employer or OSHA. If a worker has been retaliated against for 

using their rights, they must file a complaint with OSHA as soon 

as possible, but no later than 30 days.

For additional information, see OSHA’s Workers page.

How to Contact OSHA

For questions or to get information or advice, to report an 

emergency, fatality, inpatient hospitalization, amputation, or loss 

of an eye, or to file a confidential complaint, contact your nearest 

OSHA office, visit www.osha.gov or call OSHA at 1-800-321-

OSHA (6742), TTY 1-877-889-5627.

This is one in a series of informational fact sheets highlighting OSHA programs, policies or standards. It does not impose any 

new compliance requirements. For a comprehensive list of compliance requirements of OSHA standards or regulations, refer 

to Title 29 of the Code of Federal Regulations. This information will be made available to sensory-impaired individuals upon 

request. The voice phone is (202) 693-1999; teletypewriter (TTY) number: 1-877-889-5627.

DSG FS-3836 11/2015