Quick answer
A refrigerant leak in a house is rarely an emergency, but it is not harmless. R-410A is non-flammable and low in toxicity, yet it displaces oxygen in a small closed room; R-32 and R-454B are mildly flammable (A2L). Open windows, keep flames and sparks away, shut the system off and call an ODP-certified technician. No carbon monoxide alarm detects refrigerant.
Whether a refrigerant leak in your house is dangerous comes down to three things: which refrigerant is in the system, how fast it is escaping and how small the room is. Most leaks are pinholes that take weeks to empty a system, and those harm the equipment and your hydro bill long before they harm you. A fast leak into a closed mechanical closet is a different situation.
Which refrigerant is in your system, and what that changes
- R-410A, in most air conditioners and heat pumps installed from about 2010 to 2024: classed A1, meaning non-flammable and low in toxicity. Its hazard is displacement: enough of it in a small closed room pushes out the air you breathe. See R-410A in the glossary.
- R-32 and R-454B, in equipment sold new from 2025: classed A2L, meaning low toxicity and mildly flammable. They are hard to ignite and burn slowly, but an open flame or a strong spark in a pocket of leaked gas can do it. Our A2L refrigerant guide covers the change.
- R-22, in systems older than about 2010: non-flammable, with the same displacement hazard.
The rating plate on the outdoor unit names the refrigerant and the charge weight. Refrigerant vapour is heavier than air, so it sinks and collects low. Leaked into a whole house through the ducts, a residential charge dilutes to a low concentration; the risk concentrates where the indoor coil sits in a tight space, such as a condo fan-coil closet, a furnace room with the door shut, or a small basement bedroom with a ductless head.
Symptoms of refrigerant exposure in people and pets
- Dizziness, headache, light-headedness or nausea: signs of breathing air with refrigerant in place of oxygen. They should clear in fresh air.
- A racing or irregular heartbeat, fainting or trouble breathing: call 911. High concentrations affect the heart.
- Frostbite: liquid refrigerant escaping a line boils at around -50 °C and freezes skin and eyes on contact. Never put a hand on a hissing or frosting fitting.
- Pets at floor level: a dog, a cat or a caged animal on the floor breathes the densest layer first. Move them out of the room before you do anything else.
- A sharp, acrid smell near a gas flame: refrigerant drawn through a burner breaks down into irritating acidic gases. Leave that room and ventilate.
It is not carbon monoxide, and no alarm in your house detects it
Carbon monoxide comes from burning fuel; refrigerant is a chemical sealed inside copper tubing. A CO alarm, a smoke alarm and a natural gas detector all ignore it. Refrigerant is close to odourless, with at most a faint sweet or chemical smell near a large leak, so the usual evidence is mechanical: hissing or bubbling at the coil, oily residue on a fitting, ice on the larger copper line, or an air conditioner that runs without cooling.
Many new A2L systems carry their own sensor at the indoor coil, which shuts the compressor off and runs the blower to dilute a leak. If the fan on a new system is running by itself with the cooling off, leave it running and call. The slower symptoms are listed in the signs of an AC refrigerant leak.
What to do if you suspect a refrigerant leak
- Set the thermostat to Off so the compressor stops pumping refrigerant out through the leak.
- Open windows and doors in the room with the indoor unit, and prop the mechanical room door open.
- With R-32 or R-454B, put out candles and do not smoke or run a space heater nearby until the room has aired out.
- Keep children and pets out of low, closed rooms near the leak.
- Do not tighten fittings or add refrigerant from a can. Handling refrigerant in Ontario requires an ODP card.
The decision rule: symptoms in a person or a pet mean fresh air and 911. A hissing line, a visible spray or a frosted fitting means system off, windows open and a technician the same day. Weak cooling with no sound or smell can wait for a booked visit, with the system left off so the compressor is not run short of refrigerant.
What a refrigerant leak repair costs
- Diagnostic fee: $90–$150, usually credited toward the repair if you go ahead.
- Refrigerant leak repair and recharge: $300–$800+, because finding and sealing the leak costs more than the refrigerant itself.
- Most other AC repairs found on the same visit: $150–$800 depending on the part.
A proper repair finds the leak, fixes it, pressure-tests the system and recharges it by weight. Topping up a leaking system only vents more refrigerant over the following months. On an old R-22 unit with a leaking coil, replacement is usually the better use of the money, and AC refrigerant leak repair explains how we decide.
ZK Mechanical's technicians carry ODP cards and leak-detection equipment, and you get the price in writing before the repair. For AC repair in Burlington, Oakville, Mississauga or Hamilton, call (647) 801-1252 or describe what you are hearing or smelling and we will tell you whether it can wait.