Overview
The Accredited Certification Scheme (ACS) is the UK's nationally recognised route for gas engineers to prove competence in gas safety. Gas Safe Register, the official gas registration body for the UK and Isle of Man, requires evidence of a current ACS certificate (or an accepted equivalent such as an ACS-aligned NVQ/SVQ) before an engineer can register and legally work on gas appliances.
Who can apply
ACS assessment is for practising or trainee gas engineers who want to join or renew their place on Gas Safe Register. There is no single academic entry requirement; candidates are assessed on practical and theoretical competence in the categories they want to work in.
Exam pattern
ACS covers six main categories: Domestic Natural Gas, Commercial Heating, Commercial Catering, Commercial Laundry, Emergency Service Provider and Metering (ESP), and LPG. In each category, candidates must first pass a core gas safety assessment before taking individual appliance assessments (for example, central heating boilers, cookers, or gas fires). Assessment combines multiple-choice theory, written theory and practical, hands-on tests. The first-time (initial) assessment is more extensive than a later re-assessment.
Marking and results
Candidates must achieve a pass in both the relevant core assessment and each individual appliance assessment they are certifying in. ACS certificates are valid for five years; re-assessment can be taken up to six months before expiry to keep registration continuous.
How to apply
Candidates book ACS assessments through a UKAS-accredited ACS awarding/assessment centre. After passing, the certificate is used as evidence when applying to join or renew registration with Gas Safe Register.
FAQs
How long does an ACS certificate last?
Five years. Engineers must re-assess before it expires to stay on Gas Safe Register.
Can I take appliance assessments without the core assessment?
No. In every category, the core gas safety assessment must be passed first, before individual appliance assessments can be taken.