Every refrigerant a settlement can use is dangerous in at least one of four ways: it poisons, it burns, it displaces breathable air, or it is held at a pressure that can burst the pipe. Site the plant outdoors or in a separate ventilated building, never work on it alone, find leaks with soapy water and never with a flame, and assume that a kilogram of ammonia escaping into a closed 30 m³ room reaches a concentration far above a fatal level.
Part of Refrigeration
The hazards of refrigeration plant in general, with ammonia and pressure treated in their own pages: poisoning, fire, asphyxiation, cold burns and bursts.
Four Hazards Cover Every Refrigerant In This Tree
| Hazard | How it harms | Where it shows |
|---|---|---|
| Toxicity | Irritates or damages eyes, throat and lungs | Ammonia, sulfur dioxide |
| Fire and explosion | Vapour and air burn or explode | Ether, propane, ammonia in a band |
| Asphyxiation | Displaces breathable air, no warning | Carbon dioxide, and any heavy vapour in a pit |
| Pressure | Stored energy of the contents | Every charged circuit |
A fifth, minor hazard comes with all of them: liquid refrigerant leaving a restriction is far below freezing and burns skin on contact. Working Fluids compares the fluids, Ammonia Toxicity treats the one this tree builds around, and Pressure Vessels treats burst risk.
Rules That Apply To Every Plant
- Site it outdoors or in a separate, ventilated building, away from living quarters and from the cold rooms people walk into.
- Never work on a charged circuit alone, and never enter a space that smells of leak without a second person and a clear way out.
- Find leaks with soapy water on the joints. Never with a flame, whatever the fluid. A flame near a flammable vapour ignites it.
- Know where vapour collects. Heavier-than-air vapours (propane, sulfur dioxide, ether, carbon dioxide) sink to floors and pits; ammonia vapour at room temperature rises, but a cold release from a pressurised liquid can stay low at first.
- Keep water and an eyewash supply near the plant.
- Keep the relief device on the high side and never defeat it.
- Label the circuit with the fluid it holds and the materials it must never touch.
Worked Example: One Kilogram In A Closed Room
Inputs: 1 kg of ammonia released into a closed room of 30 m³.
- Moles of ammonia: 1,000 g ÷ 17 g/mol = 58.8 mol (molar mass 14 + 3 = 17).
- Volume as gas at about 20 °C, taking about 24 litres per mole (a recalled figure, flagged): 58.8 × 24 = 1,412 litres, or 1.41 m³.
- Concentration if fully mixed: 1.41 ÷ 30 = 0.047, which is 4.7% or about 47,000 ppm.
- Against the carrier’s 2,500 ppm figure for a fatal 30-minute exposure: 47,000 ÷ 2,500 = 18.8 times higher.
- Against the carrier’s flammable band of 15 to 28%: 4.7% is below the bottom of the band.
So the leak is not a fire hazard in that room, but it is far beyond fatal as a poison. The mixed concentration is the average; near the leak it is higher. The comparison shows why a plant is placed outdoors: a charge that is small as a chemical quantity becomes lethal in a small closed space.
Common Mistakes
- Relying on smell alone. It tells you something is wrong; it does not tell you whether you have time.
- Going back in for someone. Move out and upwind first and raise help; a second casualty helps nobody.
- Hunting a leak with a flame. Older practice did; do not.
- Storing refrigerant cylinders or spare charge indoors, near living quarters.
Safety
A fault is the moment of greatest danger
On any sign of a leak, cut the heat or power first, then ventilate and evacuate upwind. For skin or eye contact, flush with large amounts of water for at least 15 minutes, as the carrier says, and get help for any breathing difficulty. Do not give treatment beyond that; this page is not a medical protocol. The plant’s relief device, outdoor siting and a second person present are the controls that matter before a fault happens.
What’s Next
- Learn next: Ammonia Toxicity — ventilation, detection and response for the main fluid
- Combine with: Pressure Vessels — burst risk and the relief device