Rules desk · chart page
Air conditioning servicing: leak checks and owner jobs
Air conditioning servicing in the UK becomes a legal leak check once a system holds 5 tonnes CO2e of refrigerant, due at least every 12 months.
By the Cooler Indoors desk · figures checked · 4 charts · sources · methods
Air conditioning servicing in the UK splits into two parts. A few simple jobs belong to the owner. Everything that involves refrigerant belongs to an F-gas engineer, and above a set size the law says how often that engineer must check for leaks.
Source: GOV.UK, Checking F gas equipment for leaks · checked 29 October 2026
How we read this Maximum gap between leak checks for stationary air conditioning and heat pumps in Great Britain. Fitting automatic leak detection doubles each interval. Systems under 5 t CO2e have no set interval.
Show the numbers
| Label | months | Note |
|---|---|---|
| 5 to under 50 t CO2e | 12 | |
| 50 to under 500 t CO2e | 6 | |
| 500 t CO2e or more | 3 |
When does air conditioning servicing become a legal leak check?
When the refrigerant in the system adds up to 5 tonnes of CO2 equivalent or more. From that point GOV.UK guidance requires a check at least once every 12 months, rising to every 6 months from 50 t and every 3 months from 500 t. Not having the right checks, or leaving a leak unfixed, is a breach that can bring a civil penalty.
The duty falls on the user of the equipment as well as on the technician. For a homeowner that means booking the visit, not doing it.
How do you work out tonnes of CO2 equivalent?
Multiply the refrigerant mass in tonnes by its global warming potential. The government method notes that the label on the equipment usually gives the charge in kilograms, so divide by 1,000 first. The potentials come from the retained F-gas regulation: 675 for R32, and 3 for propane, listed in Annex IV as R290.
Source: legislation.gov.uk, Regulation (EU) 517/2014 Annex I as retained in GB · checked 29 October 2026
How we read this Worked example, not a measurement: 3 kg multiplied by each gas's GWP (2,088, 675 and 3) and divided by 1,000. Real systems hold whatever the data plate says; 3 kg is chosen because GB's small single-split rules use it as a dividing line.
Show the numbers
| Label | t CO2e | Note |
|---|---|---|
| R410A, 3 kg | 6.26 | Over the 5 t line |
| R32, 3 kg | 2.03 | |
| R290, 3 kg | 0.009 |
Does a small R32 split need yearly leak checks?
Often not by law. A 5 t threshold equals about 2.4 kg of R410A, the guidance says, but takes roughly 7.4 kg of R32 by our arithmetic. A split holding 3 kg of R32 works out at about 2 t CO2e, well under the line, so the compulsory 12-month check would not apply. Look at the outdoor unit's plate, or ask the engineer to work it out for you.
Older R410A kit is different. Even a modest charge can cross the line, and our R32 and R290 comparison sets out why new small splits in Great Britain can no longer use it.
On video: How to Clean Your Air Conditioner Filter | Mitsubishi Electric MSZ-AP Series
“How to Clean Your Air Conditioner Filter | Mitsubishi Electric MSZ-AP Series”, a video from the Mitsubishi Electric Australia channel on YouTube. Mitsubishi Electric's official owner how-to for a wall-mounted split: remove the front panel, vacuum or wash the filters, and replace the anti-allergy filter yearly. This is the owner-level job the page allows. It is their video, not ours, and it loads from YouTube only when you press play.
Source: GOV.UK, Checking F gas equipment for leaks · checked 29 October 2026
How we read this The R410A mass is printed in the GOV.UK table. The R32 mass is our worked example: 5,000 kg CO2e divided by a GWP of 675. Both mark the point where a 12-month check becomes compulsory.
Show the numbers
| Label | kg | Note |
|---|---|---|
| R410A | 2.4 | GOV.UK figure |
| R32 | 7.4 | Worked example |
What can a homeowner do between engineer visits?
Four things, and nothing beyond them. If the unit behaves oddly, switching it off at the isolator and calling the installer is the right response, not opening it up. Switch the unit off at its isolator or breaker before touching it. Clean or rinse the filters exactly as the maker's manual says. Keep leaves and clutter away from the outdoor unit. Check the condensate drain is not blocked.
Panels, wiring, pipe joints and refrigerant are all off limits. A split system's refrigerant circuit may only be opened, topped up or recovered by a qualified F-gas technician employed by a certified company. Our page on engineers and electricians covers how to check those credentials.
| Job | Who | How often |
|---|---|---|
| Isolate power before any owner task | Owner | Every time |
| Clean or rinse filters | Owner | As the maker's manual says |
| Keep outdoor unit clear, check drain | Owner | Regularly |
| Leak check, 5 t CO2e or more | F-gas engineer | At least every 12 months |
| Repair a leak and re-test | F-gas engineer | Repair at once; re-test within a month |
| Electrical faults | Registered electrician | When needed |
What happens if an engineer finds a leak?
It must be repaired as soon as possible and the system tested again within a month to prove the fix. Ask for a written note of where the leak was, what was repaired and the date of the follow-up test, and keep it with the installation paperwork so the next engineer can see the history. The duty is to fix the leak, not simply replace the gas that escaped.
Source: GOV.UK, Checking F gas equipment for leaks · checked 29 October 2026
How we read this Kilograms of R410A equal to 5, 50 and 500 t CO2e, as tabled by GOV.UK. The 6- and 3-month bands are shown for scale.
Show the numbers
| Label | kg | Note |
|---|---|---|
| 12-month band starts | 2.4 | |
| 6-month band starts | 24 | |
| 3-month band starts | 240 | Detection must be fitted |
Are hermetically sealed units treated differently?
Yes. Hermetically sealed systems have no maximum interval unless they hold 10 t CO2e or more, double the usual starting point. Separately, movable units sold in Great Britain must already use refrigerant with a GWP of 150 or less.
Questions this data raises
Who is legally responsible for arranging leak checks on a home air conditioner?
GOV.UK shares responsibility between the user of the equipment and the service technician. In practice the owner books an F-gas engineer when the system's CO2e makes a check compulsory.
Does automatic leak detection change the timetable?
Yes. It doubles the allowed gap, so a 5 t CO2e system needs checking every two years rather than every year.
Can I top up the refrigerant if the unit stops cooling?
No. Refrigerant work needs an F-gas qualified engineer, and any leak has to be found, repaired and re-tested within a month.
How do I find the refrigerant charge of my unit?
Look for the data plate on the outdoor unit, which normally lists the refrigerant type and mass in kilograms, then multiply by its GWP and divide by 1,000.
Sources for this page
- GOV.UK, Checking F gas equipment for leaks gov.uk
- government method gov.uk
- R32 legislation.gov.uk
- Annex IV legislation.gov.uk
- certified company gov.uk
All checked 29 October 2026. How we choose and read sources: Methods & sources.