Ammonia (R-717) Gas Detection

With zero global warming potential (GWP) and ozone depletion potential (ODP), ammonia is considered one of the most cost effective, energy efficient, natural refrigerants for industrial refrigeration. However, ammonia is classified as a B2L refrigerant, which means it is toxic and flammable. As such, ammonia gas detection is critical for on-site safety.

Ammonia safety


Safety is paramount for ammonia refrigeration systems. Ammonia is corrosive and human exposure will result in a chemical type burn. As ammonia is extremely hygroscopic (rapidly absorbing moisture), it readily migrates to moist areas of the body such as eyes, nose, throat and lungs. Even low levels of ammonia gas is harmful which is why strict compliance is required.

Concentration/Time Effect Compliance
0-25 ppm Low odor threshold for most people, slight irritation to eyes and breathing tracts.
25 ppm TWA 8 hour TWA NIOSH
35 ppm STEL 15 minute reference period NIOSH
50 ppm TWA 8 hour TWA, perceptible eye and throat irritation OSHA
50-100 ppm Swollen eyelids, conjunctivitis, nausea / vomiting, irritated throat
300 ppm IDLH Immediate danger to life and health NIOSH, OSHA

TWA = time weighted average
STEL = short term exposure limit
IDLH- Immediately dangerous to life of health


Ammonia is considered a flammable hazard between concentrations of approximately 15% to 28% by volume in air. EN 378 stipulates that for flammable levels of ammonia, alarms should be set as follows:

  • At low alarm level 500 ppm (0.33% lower exposure limit (LEL)) alarm and mechanical ventilation to be activated
  • At high alarm level 30,000 ppm (20% LEL) refrigerating system to be automatically stopped

Guidance following the withdrawal of HSE’s PM81 publication, “Safe Management of ammonia refrigeration systems” for the food and drinks industries and other workplaces, states levels of 500 ppm for fan ventilation and alarm and a “practical” shut down level of 6.6% LEL or 10,000 ppm.

Ammonia Safety Compliance with Greenyard Frozen

With 20 tons of ammonia on site to support its packing lines and blast freezers, effective gas detection is a top priority for Greenyard Frozen. Learn how Bacharach helps this food processor protect its personnel while providing robust data-driven notifications. Read More

Ammonia leak detection

Considering the hazardous nature of Ammonia, clear instructions ensure that a properly designed, constructed, operated, and maintained ammonia refrigeration system can be safely achieved.

The EPA states two requirements relative to leak detection::

  • Maintain a leak-free ammonia refrigeration system. Investigate all reports of an ammonia odor and repair all leaks immediately.
  • Consider installing ammonia detectors in areas where a substantial leak could occur if the facility is not manned 24 hours/day.

In addition, The International Institute of Ammonia Refrigeration (IIAR) provide codes and standards in their document: “Ammonia Leak Detection in Refrigeration Systems (2004)”.

Leak detection alarm levels and required responses vary depending on where the refrigeration equipment is installed, summarized as:

Room Type Alarm levels and actions
Compressor room alarm 25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room
150ppm: emergency ventilation activated
Compressor room shutdown 10,000ppm: Redundant emergency ventilation
20,000ppm: De-energize pumps, compressors and valves that are normally closed
Refrigerated area 25ppm: alarm to monitored location
35ppm: close liquid and hot gas solenoid valves
Packaged systems 25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room
Machinery under 100HP and Equipment Pots (not located in Machine Rooms) 25ppm: alarm to monitored location and horn strobe outside each entrance and inside the compressor room
25ppm: close liquid and hot gas solenoid valves,
25ppm: de-energize pumps, motors and non-emergency fans
25ppm: Emergency ventilation

Ammonia leak detectors

Bacharach offers a wide range of ammonia safety gas detection solutions. These innovative solutions are designed for extreme temperature refrigeration environments and provide robust refrigerant safety compliance. The Multi-Zone aspirated system provides industry leading low-level leak detection and the MGS-400 and MGS-550 diffusion systems offer exceptional low level temperature performance down to -40ºF/C.

Deciding which system is right for you depends on the total number of sampling areas, ammonia levels you want to detect, sampling frequency, integration with BMS / BAS control systems, maintenance requirements, and CAPEX and associated OPEX cost.

Multi-Zone MGS-400 Series MGS-550
Multi-Zone MGS-400 Series MGS-550 Series
Integration with BMS / BAS control system Modbus, BACnet, LonWork and analog communications Modbus, Digital and analog communications Modbus, Digital and analog communications
Temperature Zone / Application Low and Medium Low and Medium Low and Medium
Sensing Medium Infrared Electrochemical (EC), Catalytic Bead (CAT) Electrochemical (EC), Catalytic Bead (CAT) or Semi Conductor (depending on PPM alarm range)
Remote placement of sensors / sample points Up to 1200ft from leak detection monitor MGS-460: 5m from transmitter MGS-410 with MGS-402: 1,000m from transmitter 5m from transmitter
Sensor Typical Life Span Up to 10 years Up to 7 years Up to 7 years
Maintenance (functional test / calibration) Annual Annual Annual
Sensor Hot Swap N/A Plug and play pre-calibrated sensor modules for quick, simple sensor replacement Plug and play pre-calibrated sensor modules for quick, simple sensor replacement
Sensor channels 4 - 16 1 2
Sensor Range 25 - 10,000 ppm on one sensor 0-100 PPM
0-300 PPM
0-1,000 PPM
0-10,000 PPM
0-100% LEL
0-100 PPM
0-500 PPM
0-1000 PPM
0-10,000 PPM
0-100% LEL
User Interface Large graphic LCD display and on-board controls Mobile app interface with Bluetooth connectivity On board controls and LCD screen
Find out more Find out more Find out more

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