TM44 vs F-Gas: What Is the Difference?

If you are a facilities manager, managing agent or business owner with air conditioning in a commercial building in London, you have two separate legal obligations that are often lumped together as “AC compliance”. They are not the same thing. One is about energy efficiency, the other is about refrigerant leaks, and they have different triggers, different intervals and different paperwork.

The short answer

A TM44 inspection is a five-yearly energy efficiency assessment of the whole air conditioning installation, required where the building's total cooling output is over 12kW. An F-Gas leak check is a refrigerant containment check on each individual system, required at intervals set by how much refrigerant that system holds. You can need both, either, or neither, and the person responsible for both is the operator of the equipment, not the contractor.

TM44: the energy efficiency inspection

TM44 comes from the Energy Performance of Buildings (England and Wales) Regulations 2012. The obligation applies when the combined effective rated output of the air conditioning in a building exceeds 12kW, which in practice means most offices, hotels, shops and mixed-use buildings with more than a couple of split units. The inspection must be carried out by an accredited energy assessor, repeated at least every five years, and the report lodged on the national register. It assesses the sizing of the plant against the cooling load, the condition and efficiency of the equipment, the controls and how they are used, and gives recommendations for improvement. It does not require the assessor to open the refrigerant circuit. Our TM44 inspection page covers the process in detail.

F-Gas: the refrigerant leak check

F-Gas comes from the Fluorinated Greenhouse Gases Regulations 2015. It applies to any stationary air conditioning, refrigeration or heat pump system containing fluorinated refrigerant above 5 tonnes CO2 equivalent, which for common refrigerants is roughly 2 to 3 kg of gas. Above that threshold the operator must have the system leak checked by a certified engineer at an interval set by the charge: at least every 12 months for the smallest systems, every 6 months above 50 tonnes CO2e, every 3 months above 500. Systems with automatic leak detection get double the interval. The engineer and the company must both be certified; Mainteniq's company certification is REFCOM REF1024168. Our F-Gas compliance page explains the thresholds and certification.

Side by side

• Purpose. TM44 assesses energy efficiency. F-Gas prevents refrigerant leaks.
• Trigger. TM44: total building cooling over 12kW. F-Gas: any single system over 5 tonnes CO2e of refrigerant.
• Interval. TM44: every five years. F-Gas: every 3, 6 or 12 months depending on charge.
• Who does it. TM44: an accredited energy assessor. F-Gas: a certified engineer from a certified company.
• Record. TM44: a lodged inspection report. F-Gas: a per-system log of every check, every top-up and the certificates of who did the work, kept for five years.
• Penalty. Both are enforced with fines, TM44 by the local authority trading standards, F-Gas by the Environment Agency, and neither can be delegated to the contractor.

Where buildings get caught out

The usual failure is not ignorance of either regulation but the assumption that the maintenance contractor is handling both. A general HVAC contractor who is not F-Gas certified cannot legally do the leak check, and a TM44 needs a separately accredited assessor. So a building can have a service contract in place and still have no valid TM44 and no F-Gas log. The second failure is records: the leak check was done but nothing was written down, which on inspection is the same as not having done it.

The practical approach

Put both inside one maintenance contract with a contractor that holds F-Gas company certification and works with an accredited TM44 assessor. The annual F-Gas leak check and the annual service are then the same visit, the TM44 is scheduled into year five and tracked, and both records live in one file the facilities manager can produce on request. That is how Mainteniq runs it for commercial clients across Greater London; our maintenance contracts page explains what is included, and our air conditioning page covers the servicing itself.