Table of Contents

Introduction

Ammonia (NH3) is everywhere in modern industry — and everywhere it is stored, compressed or refrigerated, it demands serious gas detection. In large cold-storage, food-processing and district-cooling plants it is the working refrigerant, known as R717. In fertilizer, nitrogen-chemical and urea plants it is both a feedstock and a product. It is corrosive, pungent, flammable in air at higher concentrations, and toxic at low ones. For EHS managers operating across Russia and the Middle East, a properly sited ammonia gas detector is the difference between a contained leak and a refrigerant-room evacuation or a fertilizer-plant incident.

This guide explains ammonia’s hazards and exposure limits, where leaks occur, how electrochemical NH3 sensors behave, and how to combine fixed and portable detection. Regulatory framing follows EAC (TR CU 012/2011), ATEX and IECEx rather than US-only rules.

Ammonia’s Dual Nature: Toxic and Flammable

Ammonia is a colourless gas with a sharp, penetrating odour that most people detect at roughly 5 ppm. That odour is a useful early warning — but it is not a reliable one, because fatigue and adaptation dull the sense of smell within minutes. At low concentrations ammonia irritates the eyes, skin and respiratory tract; at high concentrations it burns the lungs and can be fatal.

Ammonia is also flammable in air. Its lower and upper explosive limits are wide enough to matter in refrigeration machine rooms and ammonia tanks, so the same detector often monitors both toxicity (ppm) and flammability.

Reference body / property	Limit	Value (ammonia)
OSHA PEL (29 CFR 1910.1000)	8-hour TWA	50 ppm
ACGIH TLV	8-hour TWA / STEL	25 ppm / 35 ppm
NIOSH IDLH	Immediately dangerous to life or health	300 ppm
Flammable range in air	LEL / UEL	15 – 28 vol%

Typical practice sets a low ammonia alarm near the TLV (25–35 ppm) and a high alarm well below the 300 ppm IDLH, interlocked with ventilation and, where required, refrigerant isolation.

Where Ammonia Leaks Happen

Refrigeration machine rooms: compressors, oil separators, suction lines and pump-out units handling R717.
Cold-storage and food-processing halls, blast freezers and ammonia evaporators in the ceiling.
Ammonia receiver tanks, accumulators and pump rooms.
Fertilizer and urea plants: synthesis loops, storage tanks, loading and rail/wagon filling.
NOx selective catalytic reduction (SCR) systems where ammonia is dosed into flue gas.
Cold-boxes and winterised outdoor equipment in Russian service; hot machine rooms in the Gulf.

Ammonia is lighter than air, so leaks tend to rise and accumulate near ceilings and in enclosed upper spaces — but in a cold room the cold, ammonia-laden air can stratify and linger. Detectors should be placed at the likely leak point and at breathing height near operators.

How Electrochemical Ammonia Sensors Work

ppm-level ammonia detection uses electrochemical (fuel-cell) sensors that generate a current proportional to NH3 concentration. They are selective enough for refrigeration and fertilizer service and respond in seconds. Users must watch two behaviours: ammonia sensors are prone to interference from amines and high humidity, and they drift toward the end of a two- to three-year cell life.

Bump test before each shift and calibrate at least every six months with certified ammonia span gas. Because ammonia is corrosive, detectors in fertilizer and SCR service may need more frequent service and a protection filter against dust and aerosols.

Fixed vs Portable Ammonia Detection

A refrigeration machine room or ammonia tank farm is a fixed-detection zone. The HD9300 fixed ammonia transmitter mounts near compressors and receivers, sends 4–20 mA / RS485 / MBUS straight to the plant DCS/PLC, and switches dual alarms and forced ventilation through the controller. Its Ex d IIC T6 Gb enclosure and –40 °C to +70 °C range suit both Siberian cold rooms and Gulf machine halls.

See the fixed detector: HD9300 Fixed Gas Detector with LCD Display

See the controller: HD6000 Fixed Gas Alarm Controller (2–128 channels)

Maintenance technicians and entry into confined refrigeration equipment need portable detection. A single-gas NH3 portable such as the HD600, or a four-in-one HD620 for mixed oil-and-gas and refrigeration duties, gives the worker a personal ppm-level alarm. The HD620 measures H2S, CO, O2 and LEL; the HD600 is a dedicated single-gas instrument with LCD display.

See the portable detector: HD600 Single-Gas Portable Gas Detector

For a small refrigeration room or equipment corner, the HD6100 single-point wall-mounted all-in-one controller brings detector, display and local alarm into one enclosure.

Hangwei Ammonia Detection Solutions

Henan Hangwei Sensing Technology Co., Ltd. has more than 20 years of manufacturing experience, 20 patents and 10 production lines. We supply fixed and portable ammonia detectors, controllers and custom sensor packages for EAC, ATEX and IECEx-oriented refrigeration and fertilizer projects, with OEM/ODM and global distributor recruitment.

Fixed NH3 detection: HD9300, Ex d IIC T6 Gb, –40 to +70 °C, 4–20 mA/RS485/MBUS, dual relays, IR remote calibration.
Portable NH3 detection: HD600 single-gas, or HD620 four-in-one for mixed duties.
Controllers: HD6000 from 2 to 128 channels; HD6100 single-point all-in-one.
Custom packages: ammonia-specific ranges, dust-protected sensors and detector-plus-controller systems.

FAQ

What is the IDLH for ammonia?

300 ppm, per NIOSH. Above this concentration a worker could not escape without irreversible harm; high alarms should trigger well below it.

Is ammonia flammable?

Yes, in air ammonia is flammable between roughly 15 and 28 vol%. Machine rooms and ammonia tanks therefore need both toxic (ppm) monitoring and an awareness of flammable range.

Can I rely on the smell of ammonia?

No. Most people smell ammonia near 5 ppm, but the sense adapts within minutes, and at high concentrations it is paralysing. Odour is a supplement, never a substitute, for calibrated detectors.

Why is ammonia used as a refrigerant if it is so hazardous?

R717 ammonia has excellent thermodynamic efficiency, is cheap and has no ozone-depletion or global-warming impact. Properly designed, detected and ventilated systems make it a safe, energy-efficient choice — which is exactly why reliable NH3 detection is mandatory.

How often should ammonia sensors be calibrated?

Bump test before each shift; full calibration at least every six months with certified NH3 span gas, more often in corrosive fertilizer or SCR service.

Where should ammonia detectors be mounted?

Near the likely leak source (compressors, receivers, valves) and at operator breathing height. Because ammonia is lighter than air, also monitor upper spaces; in cold rooms, test at multiple levels due to stratification.

Get Expert Guidance

Ammonia detection in refrigeration and fertilizer plants is a safety-critical, code-driven system. Hangwei Sensors designs and manufactures fixed and portable NH3 detectors and controllers for cold storage, food processing, fertilizer and SCR applications across Russia, the Middle East and worldwide. Contact our engineers for detector siting, alarm set-points, EAC/ATEX documentation and OEM or distributor terms.

Email: hw@hangweisensors.com | Phone: +86 371 6667 0886

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