Biagio Malacaria died three weeks after being set alight while draining a vehicle’s fuel system at Alexanders of Twickenham, an MoT, service and repair workshop.
Last week the City of London Magistrates Court found Alexanders guilty of failing to ensure the safety at work of its employees.
It imposed the maximum fine possible in a magistrates court for the offence, and ordered the firm to pay costs of £16,905.
The court was told that Mr Malacaria had been working with woefully inadequate equipment.
HM Inspector of Health and Safety Andrew Withers said: “The company failed in its duties in a number of ways including having no risk assessment for fire and explosions, a lack of safety measures for this type of work and failing to ensure that all staff were suitably trained.”