Ammonia (Anhydrous)

Classification

Flammable gas, Category 2; Gas under pressure (liquefied gas); Acute toxicity (inhalation), Category 3; Skin corrosion, Category 1B; Hazardous to the aquatic environment (acute), Category 1

Hazard statements

• H221 Flammable gas.
• H280 Contains gas under pressure; may explode if heated.
• H314 Causes severe skin burns and eye damage.
• H331 Toxic if inhaled.
• H400 Very toxic to aquatic life.

Key precautionary statements

• P210 Keep away from heat, hot surfaces, sparks, open flames and other ignition sources. No smoking.
• P260 Do not breathe gas.
• P280 Wear protective gloves, protective clothing, eye protection and face protection.
• P304+P340 IF INHALED: Remove person to fresh air and keep comfortable for breathing.
• P305+P354+P338 IF IN EYES: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
• P316 Get emergency medical help immediately.
• P377 Leaking gas fire: Do not extinguish, unless leak can be stopped safely.
• P410+P403 Protect from sunlight. Store in a well-ventilated place.

The NIOSH REL (25 ppm TWA, 35 ppm STEL) and ACGIH TLV are half the federal OSHA PEL of 50 ppm TWA, and federal OSHA has no short-term limit. Cal/OSHA is stricter than federal OSHA at 25 ppm TWA and 35 ppm STEL. No skin notation is assigned. Storage and handling of anhydrous ammonia is covered by a separate OSHA standard, 29 CFR 1910.111. State OSHA plans may set different limits.

• Appearance: Colorless gas, shipped as a liquefied compressed gas
• Odor: Pungent, suffocating
• Molecular weight: 17.0
• Boiling point: -28°F (-33°C)
• Freezing point: -108°F (-78°C)
• Flash point: Not applicable (gas). NIOSH notes ammonia does not meet the DOT flammable gas definition but should be treated as one.
• Autoignition temperature: 1204°F (651°C)
• Explosive limits: LEL 15%, UEL 28%
• Vapor pressure: 8.5 atm
• Relative gas density: 0.60 (lighter than air)
• Water solubility: 34%

Inhalation

Irritates the eyes, nose and throat. Higher exposures cause breathing difficulty, wheezing and chest pain, and can cause fluid in the lungs (pulmonary edema) with pink, frothy sputum. Severe exposure can be fatal.

Skin

Causes burns and blistering. Contact with the liquid also causes frostbite.

Eyes

Causes severe irritation and burns that can permanently damage the eyes. Liquid contact causes frostbite.

Ingestion

Not a likely route for the gas. Swallowing ammonia solutions causes burns to the mouth, throat and stomach.

Target organs

Eyes, skin, respiratory system

Gloves

Ammonia-impervious gloves such as neoprene, butyl rubber or Teflon, per manufacturer SDS. Insulated gloves are also needed where liquid contact and frostbite are possible.

Eyes and face

Chemical splash goggles, with a face shield worn over them for transfer and connection work. Contact lenses are not recommended.

Respiratory

Up to 250 ppm, a NIOSH-approved chemical cartridge respirator with ammonia cartridges. Up to 300 ppm, a full-facepiece respirator or gas mask with ammonia canister. Above 300 ppm (IDLH), unknown concentrations or emergencies, a pressure-demand self-contained breathing apparatus with full facepiece.

Clothing

Ammonia-impervious clothing and chemical boots. Provide an eyewash and quick-drench shower where solutions over 10% are handled.

Store in a cool, well-ventilated area with containers tightly closed, below 120°F (49°C), away from ignition sources and protected from physical damage. Use only stainless steel, carbon steel or black iron for containers and piping. Storage systems must meet OSHA 29 CFR 1910.111.

Only trained workers should connect, transfer or vent ammonia. Keep emergency eyewash and drench water available, check hoses and valves before use, and stand upwind during transfers.

Keep away from

• Strong oxidizers
• Acids
• Halogens
• Salts of silver and zinc
• Copper and galvanized surfaces (corroded by ammonia)

• Evacuate and isolate the area. Move upwind and to the side of the release.
• Only trained responders with full protective equipment and self-contained breathing apparatus should approach the leak.
• Stop the leak if it can be done safely.
• Use water spray downwind to absorb the gas. Do not spray water directly on the container or on liquid ammonia, which increases vapor release.
• Keep runoff out of drains and waterways.
• Follow ERG Guide 125.

Suitable extinguishing media

• Water spray or fog
• Dry chemical
• Carbon dioxide
• Foam

Special hazards

Stop the gas flow before putting out the fire. Containers exposed to heat may rupture if relief valves fail; cool them with water spray from a safe distance. Ammonia is hard to ignite outdoors, but in confined spaces, especially with oil or other combustibles present, it can burn or explode. Burning produces toxic nitrogen oxides. Firefighters need full protective clothing and positive-pressure self-contained breathing apparatus.

• OSHA Hazard Communication (29 CFR 1910.1200): Hazardous chemical. Labels and safety data sheets are required.
• OSHA Storage and Handling of Anhydrous Ammonia (29 CFR 1910.111): Design, construction and operation requirements for ammonia systems.
• OSHA Air Contaminants (29 CFR 1910.1000, Table Z-1): PEL 50 ppm (35 mg/m³) TWA.
• OSHA Process Safety Management (29 CFR 1910.119, Appendix A): Threshold quantity 10,000 lb for anhydrous ammonia.
• CERCLA (40 CFR 302.4): Hazardous substance, reportable quantity 100 lb.
• EPCRA Section 302 (40 CFR 355): Extremely hazardous substance, threshold planning quantity 500 lb, reportable quantity 100 lb.
• EPCRA Section 313 (TRI) (40 CFR 372.65): Listed. 10% of total aqueous ammonia is reportable under this listing.
• Clean Air Act 112(r) Risk Management Program (40 CFR 68.130): Threshold quantity 10,000 lb for anhydrous ammonia.
• DOT (49 CFR 172.101): UN1005, Ammonia, anhydrous, Division 2.2 for US domestic transport; packages must be marked Inhalation Hazard.

• NIOSH Pocket Guide: Ammonia
• PubChem: Ammonia GHS classification
• OSHA Annotated PELs, Table Z-1
• EPA Consolidated List of Lists (October 2024)
• Tanner Industries SDS: Anhydrous Ammonia