CPA1 is an extra competence and Safety check over and above ACS gas qualifications to ensure engineers who carry out Combustion Analysis as part of the Installation, Commission, Servicing and Maintaining of Gas Appliances can do so competently and with total regard for Health and Safety which could mean the difference between life and death where Carbon Monoxide and Gas Ommisions are concerned.
The real problem in the gas services industry has been and continues to be that until CPA1 existed there was no 'driving test' to demonstrate that engineers know how to use FGA's correctly.
There are approx 120,000 illegal gas safe workers operating in the UK.. http://www.gassaferegister.co.uk/learn/illegal_gas_workers.aspx
Make sure you are GAS SAFE !!