"Anhydrous" means "without water." The product is pure ammonia (NH₃), stored as a liquid under pressure and released as a colorless gas with a sharp, suffocating odor. It is about 82% Nitrogen by weight, which is why agriculture uses so much of it. 

What is anhydrous ammonia?

“Anhydrous” means “without water.” The product is pure ammonia (NH₃), stored as a liquid under pressure and released as a colorless gas with a sharp, suffocating odor. It is about 82% nitrogen by weight, which is why agriculture uses so much of it.  

Physical and Chemical Properties 

 Because the boiling point is so low, a liquid release flashes to vapor and chills whatever it touches. The vapor is lighter than air, but the cold aerosol cloud from a large release often hugs the ground first. 

Approximate vapor pressure of liquid ammonia in a closed container (verify against your supplier's data): 

A tank left in the sun climbs this table fast, which is why relief valves and fill limits matter. 

Common Industrial and Agricultural Uses 

• Fertilizer: Direct soil injection is the largest single use. 

• Refrigeration: Cold storage, food processing, ice rinks, and distribution warehouses run on ammonia because it is efficient and has no ozone-depletion or high-GWP problem. 

• Chemical manufacturing: Feedstock for nitric acid, plastics, explosives, and many other nitrogen compounds. 

• Water treatment: Combined with chlorine to form chloramine disinfectant in municipal systems. 

GHS classification and SDS summary 

Hazard classification 

Classifications vary slightly between manufacturers, so always confirm against the SDS you receive. A typical anhydrous ammonia SDS shows: 

• Flammable gas, Category 2. 

• Gas under pressure (liquefied gas). 

• Acute toxicity, inhalation, Category 3. 

• Skin corrosion, Category 1B. 

• Serious eye damage, Category 1. 

• Hazardous to the aquatic environment, acute, Category 1. 

The signal word is "Danger." Classification rules come from OSHA's Hazard Communication Standard.

Hazard and precautionary statements 

Common hazard statements: H221 (flammable gas), H280 (contains gas under pressure; may explode if heated), H331 (toxic if inhaled), H314 (causes severe skin burns and eye damage), and H400 (very toxic to aquatic life). 

Common precautionary statements: 

• Prevention: P260 (do not breathe gas), P271 (use only outdoors or in a well-ventilated area), P280 (wear protective gloves, clothing, eye and face protection) 

• Response: P303+P361+P353 (skin: remove contaminated clothing, rinse skin), P304+P340 (inhaled: move to fresh air), P305+P351+P338 (eyes: rinse cautiously for several minutes), P310 (call a poison center or doctor immediately) 

• Storage: P403 (store in a well-ventilated place), P410+P403 (protect from sunlight, store ventilated) 

What to check in an ammonia SDS? 

Every SDS follows the 16-section format required by HazCom. For ammonia, three sections do most of the work: 

• Section 2, Hazard Identification: 

Confirm the classification, pictograms, and H/P statements match what your labels and training say. 

• Section 8, Exposure Controls/PPE:  

Compare the listed limits and glove and respirator recommendations to the numbers in this guide and to your own hazard assessment. 

• Section 9, Physical and Chemical Properties:  

Check boiling point, vapor pressure, and flammability data, and make sure they agree with your process conditions. 

A supplier whose Section 8 lists limits that don't match Section 2's toxicity category deserves a phone call. Keeping current SDSs organized and searchable, for example, in a system like CloudSDS, makes that check routine rather than a scramble before an inspection. 

What are exposure limits? 

You may see "10,000 ppm" quoted for ammonia IDLH on older pages. That figure is wrong; it equals 1% by volume and is not the NIOSH IDLH. The limits below are the ones to use. 

• OSHA PEL 

50 ppm (35 mg/m³) as an 8-hour TWA, listed in Table Z-1 of 29 CFR 1910.1000 [1]. This is the legally enforceable limit for the general industry. 

• ACGIH STEL 

The ACGIH Threshold Limit Value is 25 ppm as an 8-hour TWA with a 35 ppm short-term exposure limit (15 minutes) [3]. TLVs are recommendations, not law, but they are stricter than the PEL and are widely used in exposure assessments. NIOSH also recommends 25 ppm TWA and 35 ppm STEL [2]. 

• NIOSH IDLH 

300 ppm [4]. At this concentration, workers could suffer serious effects or be unable to escape within 30 minutes. 

Required PPE 

Skin and eye protection 

• Eyes and face: Chemical splash goggles, non-vented or indirectly vented, with a face shield over them for transfer work. Contact lenses offer no protection and complicate eye flushing. See 29 CFR 1910.133. 

• Hands: Chemical-resistant gloves such as butyl, neoprene, or nitrile, chosen against the SDS and glove manufacturer data. For liquid contact, wear insulated cuffed gloves as well, since the cold alone causes frostbite. See 29 CFR 1910.138 

• Body: Long sleeves, chemical-resistant apron or suit for transfers, and rubber boots. Pant legs go over boots so liquid doesn’t run inside. 

• Program basis: Employers must assess hazards and select PPE accordingly under 29 CFR 1910.132. 

Respiratory protection 

Respirators use falls under 29 CFR 1910.134, which requires a written program, medical clearance, and fit testing. As a rule: 

• Below IDLH: An air-purifying respirator with ammonia-rated cartridges and a full-facepiece for eye protection may be appropriate. Cartridges have end-of-service limits, so set a change schedule. 

• At or above 300 ppm, unknown concentrations, or emergency entry: pressure-demand SCBA, or a supplied air respirator with an escape cylinder. 

• Warning limits: Ammonia’s odor becomes tolerable through olfactory fatigue, so smell alone is not a reliable alarm. Fixed detectors are. 

Storage and process safety requirements 

Tank design and pressure management 

OSHA's anhydrous ammonia standard, 29 CFR 1910.111, covers storage and handling and adopts ANSI K61.1 for design and construction [11]. Key points: 

• Containers must be built to ASME code for their working pressure. 

• Each vessel needs pressure relief valves, a liquid-level gauge, and a pressure gauge. 

• Never fill to 100%. Liquid needs vapor space to expand as temperatures rise. 

• Piping, hoses, and fittings must be rated for ammonia service. Copper, brass, and galvanized parts corrode rapidly and are not allowed. 

PSM coverage under OSHA 1910.119 

Ammonia, anhydrous, is listed in Appendix A of the Process Safety Management standard with a threshold quantity of 10,000 lb [5]. Above that amount in a process, you need process hazard analyses, written operating procedures, mechanical integrity programs, management of change, and compliance audits. Retail fertilizer facilities are partly exempt, so check the scope paragraph of the standard rather than assuming. 

EPA risk management program 

EPA's RMP rule, 40 CFR Part 68, sets the same 10,000 lb threshold for anhydrous ammonia [6]. Covered sites must submit a Risk Management Plan, complete a hazard assessment including worst-case release scenarios, and coordinate emergency response with the local community. PSM and RMP overlap heavily, but they are enforced separately by different agencies. 

Ventilation requirements 

• Keep indoor storage and refrigeration machinery rooms ventilated, with a mechanical system that can be triggered by detectors. 

• Place ammonia detectors at low and high points where a leak would collect and wire them to alarms. 

• Outdoor storage is preferred for bulk tanks. If the enclosure is unavoidable, keep it open enough to disperse vapor. 

• For refrigeration systems, use the ANSI/IIAR standards alongside OSHA rules. 

EPCRA and reporting obligations 

EHS Status and TPQ 

Ammonia (CAS 7664-41-7) is on the EPCRA Extremely Hazardous Substance list with a Threshold Planning Quantity of 500 lb [9]. Under Section 302, a facility that has that amount or more must notify the State Emergency Response Commission and Local Emergency Planning Committee within 60 days of first exceeding it. Releases of 100 lb or more in 24 hours (the reportable quantity) must be reported immediately to the National Response Center, SERC, and LEPC. 

Tier II Reporting 

Facilities holding ammonia at or above the reporting threshold submit an annual Tier II inventory by March 1 covering the previous calendar year, following 40 CFR Part 370. Reports include quantity ranges, storage locations, and container types. 

Transfer and field handling protocols 

Nurse tank operation 

• Towing speed is commonly limited to about 30 mph on public roads, though some state rules set lower limits. Confirm local requirements. 

• Display a slow-moving-vehicle (SMV) emblem, use safety chains, and inspect the hitch before every trip. 

• Keep an emergency water supply and protective gear with the tank, and ensure the operator knows where each item is. 

• Park on level ground away from the public and never leave a hooked-up tank unattended. 

Connection and disconnection procedures 

• Put on full PPE before touching any hose. 

• Inspect hoses and couplers for cracks, wear, or corrosion. 

• Connect and secure fittings, then open valves slowly. 

• Watch pressures and levels during the transfer. 

• Close the liquid valves first, then bleed the residual liquid from the hose before disconnecting. Stand upwind and keep your face away from the coupler. 

• Cap or plug openings and store hoses properly. 

Rushing a disconnect is how most hose-related injuries happen. The hose holds liquid even after the valve closes. 

Leak detection methods 

• Nose and eyes: Sharp odor and eye irritation are early signs but shouldn’t be your primary method. 

• Chemical indicators: Wet red litmus paper turns blue in ammonia vapor, and phenolphthalein solution turns pink. Both are useful for pinpointing small leaks. 

• Electronic detection: Electrochemical, infrared, and laser-based fixed or portable detectors give continuous readings for industrial systems. 

• Soap solution: Bubbles reveal fitting leaks in pressurized lines. 

Emergency response and first aid 

Decontamination procedures 

• Eyes: Flush with lukewarm water for at least 15–20 minutes, holding lids open. 

• Skin: Remove contaminated clothing, but do not pull off anything frozen to the skin. Flush the area with large amounts of water for at least 15–20 minutes. 

• Inhalation: Move the person to fresh air and keep them still and warm. 

• Call emergency services in every case involving liquid contact or significant inhalation. 

Medical treatment considerations 

Ammonia burns tissue on contact, and damage to eyes and lungs can worsen over hours. Anyone exposed to more than a brief whiff should be evaluated by a medical professional, even if symptoms seem to ease. Trained responders and clinicians decide on oxygen, airway support, and follow-up care. This guide is general safety information and doesn’t replace medical advice. Give your safety data sheet to emergency personnel and contact your local poison control center. 

Emergency action plan requirements 

An emergency action plan under 29 CFR 1910.38 should include: 

• Reporting procedures for fires and releases. 

• Evacuation routes and assembly points. 

• Procedures for employees who stay shut down critical operations. 

• Accounting for all employees after evacuation. 

• Rescue and medical duties for designated employees. 

• Contact names for questions about the plan. 

Sites covered by PSM or RMP have additional emergency planning requirements. Train workers, run drills, and update the plan whenever a process changes. 

DOT transport classification 

UN1005, Hazard Class 2.3 + 8 Subsidiary, Placarding 

Anhydrous ammonia ships under UN1005. Under international rules (UN Model Regulations, IMDG, ICAO, ADR), it is Division 2.3 (toxic gas) with a subsidiary hazard of Class 8 (corrosive).  

Check the domestic classification before you label a shipment: the U.S. Hazardous Materials Table in 49 CFR 172.101 lists “Ammonia, anhydrous” as division 2.2 (non-flammable gas) for domestic transport, with a division 2.2 placard, so verify the current entry for your route. Nurse tanks and cargo tanks have separate packaging rules in 49 CFR Part 173. For emergency response information, use Guide 125 in PHMSA’s Emergency Response Guidebook. 

Frequently Asked Questions 

• What is the OSHA exposure limit for anhydrous ammonia? 

over 25 ppm TWA, with a 35 ppm short-term limit. 

• Is anhydrous ammonia an EPCRA-reportable chemical? 

Yes. It is an extremely hazardous substance with a 500 lb TPQ, so facilities at or above that amount must make Section 302 notifications and file Tier II reports. Releases of 100 lb or more in 24 hours must be reported immediately. 

• What PPE is required for handling anhydrous ammonia? 

Splash goggles with a face shield, chemical-resistant gloves (cold-insulated for liquid work), protective clothing, and rubber boots. A respirator is used when concentrations exceed limits, and SCBA is required at IDLH or in emergencies. 

• Does anhydrous ammonia storage trigger OSHA PSM? 

Yes, if the process contains 10,000 lb or more. The same quantity triggers EPA's RMP rule. Certain retail and remote-facility exemptions apply, so read the scope section of the standard.