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Refrigerant leaks in commercial air conditioning: signs, costs and legal duties

Updated 23 October 2026 · SEO Dons Editorial

What are the signs of a refrigerant leak?

The clearest list is in the leak-checking rules themselves. Commission Regulation (EC) No 1516/2007, carried on legislation.gov.uk as retained law, covers stationary refrigeration, air conditioning and heat pump equipment holding 3 kg or more of F gas. It says one or more of these situations "shall constitute a presumption of leakage":

  • a fixed leakage detection system indicates leakage;
  • the equipment produces abnormal noises or vibration, ice formation or insufficient cooling capacity;
  • indications of corrosion, oil leaks, and component or material damage at possible leakage points;
  • indications of leakage from sight glasses, level indicators or other visual aids;
  • damage to safety switches, pressure switches, gauges and sensor connections;
  • deviations from normal operational conditions, including readings from real-time electronic systems.

In a building that reads as zones that stop reaching setpoint, frost or ice where it should not be, oily residue around joints, and alarms from the controller or building management system.

Context still matters. Daikin's manual for its VRV IV outdoor units says the system goes into defrost operation to remove frost from the outdoor coil in heating, so winter frost outdoors is part of normal running. A fault code is a prompt, not a diagnosis: Mitsubishi Electric's service manual for its PUHZ-SHW outdoor units gives overheated compressor operation caused by a shortage of refrigerant as one cause of its high discharge temperature code, with the action to check for leakage.

If refrigerant escapes into an occupied room, Daikin's manual says to turn off combustible heating devices, ventilate the room and contact the dealer, and not to use the system until a service person confirms the leak is repaired.

Why is topping up a known leak not a repair?

Because the law treats a detected leak as a fault to repair. Article 3 of Regulation (EU) No 517/2014, as it applies in Great Britain, says that where a leakage is detected the operator must ensure the equipment is repaired "without undue delay". GOV.UK puts it in practical terms: repair the leak as soon as possible and repeat the test within a month to check the repair worked. Where the equipment is subject to leak checks, Article 3 adds that the follow-up check must be made by a certified person within one month of the repair.

Adding gas is also F-gas work in its own right. REFCOM's FAQs define maintenance or servicing as activities that break into the refrigerant circuit, including supplying the system with gas and repairing leakages, and Article 3 requires undertakings doing that work to be certified. The guide to checking an F-gas certificate shows how to verify the company and the engineer.

The cause matters as well. The leakage-checking regulation says the cause "shall be identified as far as possible, to avoid recurrence". A top-up that restores cooling for a few weeks leaves that question open, and gas added "due to leakage" still goes in the records. GOV.UK warns that missing leak checks or unfixed leaks can bring a civil penalty. What a repair visit covers is set out on the commercial air conditioning repair page.

How often must a commercial system be leak-checked?

It depends on the charge in tonnes of carbon dioxide equivalent. Operators of equipment holding 5 tonnes or more must have it checked for leaks, and for air conditioning the checks must be carried out by certified natural persons. Article 4 sets the interval, and a leakage detection system lengthens it.

Charge (tonnes CO2 equivalent)Check at least everyWith a leakage detection system
5 to under 5012 months24 months
50 to under 5006 months12 months
500 or more3 months6 months

At 500 tonnes and above the detection system is not optional: Article 5 requires it, and requires the system itself to be checked at least every 12 months. GOV.UK's table lists that band under automatic leak detection. It also says hermetically sealed systems have no maximum period between checks unless they hold 10 tonnes or more, and that renting out equipment can make the owner responsible for the checks, depending on the rental agreement. The F-gas regulations guide covers the bands in full. Newly installed equipment must also be checked for leakage immediately after it is put into service.

How do engineers find a leak?

The leakage-checking regulation sets the order. REFCOM describes two families of method: direct checks that locate escaping gas, and indirect checks that analyse how the system is behaving.

  1. Records first. Certified personnel must check the equipment records before a leak check, paying special attention to repeating issues and problem areas.
  2. Systematic parts. Joints, valves including stems, seals including those on replaceable driers and filters, parts subject to vibration, and connections to safety or operational devices must always be checked.
  3. Direct methods. These are gas detection devices adapted to the refrigerant, with portable devices sensitive to at least five grams a year and checked every 12 months, UV detection fluid or dye, or proprietary soapsuds. UV dye is allowed only if the equipment manufacturer has approved it.
  4. Indirect methods. The engineer analyses pressure, temperature, compressor current, liquid levels or recharge volume, but any presumption of leakage must then be followed by a direct examination.
  5. Pressure testing. Before pressure testing with nitrogen or another suitable gas, the refrigerant must be recovered from the whole system by certified personnel.

What happens during a repair, and what drives the cost?

No price is given here because no official source for one was found, and a leak at an accessible joint is a different job from one in a ceiling void. Prices vary by system. What can be sourced is the sequence the regulation sets, and each step is a line a written quote should show.

  • Leak search. Time depends on how many of the listed joints, valves and seals can be reached.
  • Repair by personnel certified for that specific activity, preceded by a pump-down or recovery where necessary.
  • A pressure test with nitrogen or another suitable testing and drying gas where necessary, followed by evacuation, recharge and a leakage test.
  • Refrigerant. The type and quantity added go into the records, so the quote should state both.
  • The follow-up check within a month, which concentrates on the repaired area and adjacent areas where stress was applied. It is a second visit to price.

When the leak is inside a compressor or outdoor unit the job changes; compressor replacement costs and the repair-or-replace test covers that. Refrigerant supply rules are also moving, which the GB F-gas changes guide tracks. Readers who want repair contractors to quote can send an enquiry through the site's form.

What records must the operator keep?

Article 6 requires a record for each piece of equipment that must be leak-checked: the quantity and type of gas installed; gas added during installation, maintenance, servicing or due to leakage; gas recovered; the identity and certificate number of the undertaking that installed, serviced or repaired it; and the dates and results of every check. GOV.UK adds that records are kept for 5 years, that the operator must keep the certificate numbers of contractors used, and that the Environment Agency may ask to see the records during an inspection. REFCOM offers an F-gas logbook and a leak test record sheet as downloads.

Sources

Common questions

Is a slow loss of refrigerant acceptable on an older system?

The rules set no tolerable loss rate. Article 3 requires operators to take all measures that are technically and economically feasible to minimise leakage, and any detected leak must be repaired without undue delay. A system that needs gas added regularly is leaking.

Do systems below 5 tonnes have any leak duties?

Routine leak checks under Article 4 start at 5 tonnes of carbon dioxide equivalent, and hermetically sealed equipment below 10 tonnes is excluded if it is labelled as such. The duty to take precautions against leakage and to repair a detected leak applies to any equipment containing F gas.

Who is responsible for leak checks on a leased or shared system?

REFCOM says the person having control of the equipment, typically a company, is likely to be the operator and to carry the responsibility. GOV.UK adds that where equipment is rented out, the rental agreement may make the owner responsible instead of the end user. Check the agreement before the first check is due.

Does the same law apply in Northern Ireland?

This page covers Great Britain. GOV.UK says Northern Ireland is part of the European Union F-gas system, and organisations registered there should contact the Northern Ireland Environment Agency.

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