A Lincolnshire gas installation company and its director Martyn Crute have been fined after illegally conducting work on flue accessories in the county.
UK Oil and Gas Limited carried out gas fittings and service pipework in numerous homes, even though they were not registered with the Council for Registered Gas Installers (CORGI).
HSE inspector Sarah Jardine said: "As the director of UK Oil and Gas Ltd, Mr Crute misled vulnerable people, abused their trust and undertook work which cost one couple hundreds of pounds to put right and make safe.
In order to work legally in the UK, gas installers must be registered with the appropriate approved body, Ms Jardine warned.
She also stated that it is essential that homes and businesses check this prior to work being completed.
UK Oil and Gas Limited was handed a £6,000 fine, while Mr Crute was charged £2,000 and ordered to pay £41,000 in costs.