Refrigerant gas leaks: is it dangerous and how can you tell

A refrigerant leak is one of the more common faults behind an aircon that “used to cool fine and now does not.” It is not usually an emergency in the way a gas stove leak would be, but it is not nothing either, and knowing the signs helps you catch it before it strains other parts of the unit.

This is general safety information, not a substitute for a professional diagnosis. If you smell something strong and chemical near the unit or feel unwell in the room, ventilate the space and get a technician to check it rather than waiting.

What usually causes a leak

Refrigerant leaks rarely come from the gas itself going bad, since refrigerant does not wear out sitting inside a sealed system. The more common causes are a joint or fitting that was not sealed properly during installation, corrosion on the copper piping over years of use, and physical damage to the outdoor unit’s piping from impact or vibration. This is one reason installation quality matters well beyond the day the unit goes in: a poorly sealed joint can hold for months before it starts leaking slowly.

Signs of a refrigerant leak

• Cooling gets weaker over days or weeks, rather than failing suddenly.
• Ice forms on the indoor unit’s coil or the piping, which looks counterintuitive but is a classic low-refrigerant symptom.
• A hissing or bubbling sound near the indoor or outdoor unit, especially right after it switches on.
• Electricity bills creep up for the same usage pattern, since a low-refrigerant system works harder to reach the set temperature.
• A faint chemical or slightly sweet smell near the unit, though many refrigerants used today are close to odourless in small amounts.

Is it dangerous?

Refrigerant gas is heavier than air, so in a small, sealed room a significant leak can lower the oxygen concentration near floor level. In practice, most household leaks are slow and the volume of gas is small relative to the room, so the realistic risk is mild symptoms like dizziness or a headache rather than acute danger. The exception is a large, sudden leak in a small, unventilated space, which is where ventilating and leaving the room for a period is the sensible precaution.

What to do if you suspect a leak

1. Switch off the unit rather than letting it keep running on low refrigerant.
2. Open windows or ventilate the room if you notice any smell or feel unwell.
3. Avoid DIY gas top-ups. This needs licensed handling and proper leak detection, not a quick refill.
4. Book a gas leak repair with a technician who can pressure test the system, find the leak point, and repair it before recharging the gas.

Comparing leak severity

Sign	Likely severity	Suggested response
Gradual weaker cooling over weeks	Small, slow leak	Book a service within the week
Sudden loss of cooling, hissing sound	Larger leak	Book promptly, avoid running the unit
Strong chemical smell, dizziness in the room	Significant leak in a small space	Ventilate immediately, leave the room, then arrange a technician

Why finding the leak matters more than the top-up

Topping up refrigerant without finding and sealing the leak point is a common shortcut that only buys a few weeks or months before cooling drops again. A proper repair involves pressure testing to locate the leak, usually at a joint, valve, or a corroded section of piping, sealing or replacing that section, then vacuuming the lines before recharging. It costs more upfront than a straight top-up, but it is the difference between fixing the problem and paying for the same top-up again later. Refrigerant handling is one of the clear lines between safe DIY maintenance and a job for a licensed technician; the DIY vs professional cleaning guide breaks down what else falls on each side of that line.

If gas leaks or health and safety are your main concern when choosing a provider, aircon repair and servicing specialists on this directory are ranked with real customer feedback factored in, which is worth checking before booking a repair. The home page lists every category on this directory if you need a different kind of specialist for the same job, such as an installer to reseal a joint properly.

A note on multi-unit homes

If one unit in a multi-unit home shows leak signs, it is worth having the others checked at the same visit, especially if they were installed around the same time by the same crew. A joint sealing issue during one installation sometimes points to a pattern across all the units installed that day, rather than a one-off fault.

Details on how safety and reliability feedback shape rankings on this directory are on the methodology page.