F-gas
F-gas leak-check frequency (GB)
- where
- CO₂ equivalent (tonnes)
- refrigerant charge (kg)
- global warming potential (AR4)
Explain this equation
Works out the CO₂ equivalent of a system and then the maximum time allowed between F-gas leak checks in Great Britain. Use it when setting up a maintenance schedule.
The charge in kilograms times the GWP, divided by 1000, gives tonnes of CO₂ equivalent. The interval then comes from the regulation bands: under 5 t no mandatory check; 5 to 50 t every 12 months; 50 to 500 t every 6 months; 500 t and over every 3 months. A working automatic leak detection system doubles each interval, and hermetically sealed, labelled systems under 10 t are exempt.
The CO₂e equation sets the size of the system; the interval is a lookup against the legal thresholds rather than a formula.
Sense check: 10 kg of R404A is about 39 t, so a check every 12 months, or every 24 months with leak detection fitted.
Watch out: at 500 t and above leak detection is compulsory, not optional, and the detection system itself must be checked at least every 12 months.
Finds the maximum interval between mandatory leak checks for stationary refrigeration, air conditioning and heat pump equipment under the GB F-gas rules, from the charge and GWP.
Enter your values to see the result.
Good to know
Bands (GB, checked November 2026): 5 to under 50 t CO₂e every 12 months; 50 to under 500 t every 6 months; 500 t and over every 3 months. A working automatic leak detection system doubles each interval, and is mandatory at 500 t and over. Hermetically sealed, labelled systems under 10 t are exempt. A repaired leak must be rechecked within one month. Keep records of every check. Defra confirmed no 2026 legislation changing the phasedown steps and the leak-check bands are unchanged.
Common mistake
Basing the band on kg instead of t CO₂e, or using the factory charge only and forgetting the additional field charge.
Limits
Covers stationary RAC and heat pump equipment in England, Scotland and Wales only (not switchgear, vehicles or ORC). Northern Ireland follows EU Regulation 2024/573, which keeps the same CO₂e bands but also requires checks on HFO (Annex II section 1) charges of 1 kg or more, so this calculator does not apply there. Check the current GOV.UK guidance as the GB rules are under review.
Sources
- GOV.UK: Checking F gas equipment for leaks (5 t: 12 months, 50 t: 6 months, 500 t: 3 months; intervals doubled with leak detection; leak detection required at 500 t; hermetically sealed under 10 t exempt)
- Defra: F gas guidance for Great Britain (September 2024) – retained Regulation (EU) No 517/2014 as amended
- FETA F-gas update, 28 May 2026 (Defra will not legislate in 2026 to change the 2027 phasedown step; no change to leak-check rules)
- Linde: Refrigerants and the F-gas Regulation summary sheet (GWP per Regulation 517/2014 Annex I/IV, AR4: R32 675, R134a 1430, R404A 3922, R407C 1774, R410A 2088, R448A 1387, R449A 1397, R513A 631; kg equal to 5/50/500 t CO₂e)
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow the equipment manufacturer’s data, CIBSE guidance, BS EN 378, the F-gas Regulations and your company procedures. Refrigerant work needs the correct F-gas certification.