A man has been awarded several hundred thousand dollars in damages after being seriously burnt while working on an underground petrol tank in Canberra's north.

Phillip Raymond D'Arcy suffered burns to 33 per cent of his body when a fire started inside an underground petrol tank that he was re-lining with fibreglass on September 11, 2012.

The incident happened at the Caltex petrol station in Kaleen, when Mr D'Arcy was 44.

Mr D'Arcy successfully sued his then-employer, Fuel-Sys Installations, for damages in an ACT Supreme Court trial, but Justice John Burns found that Caltex, the other defendant, was not liable.

Justice Burns ruled that Fuel-Sys was liable for $376,600.67 in damages, covering the money Mr D'Arcy will lose in the future as a result of his injuries, and income tax he is entitled to recover on workers' compensation receipts.

Fuel-Sys was also found to be liable for Mr D'Arcy's losses since the fire, but the exact amount is yet to be determined because Justice Burns did not have access to records showing Mr D'Arcy's recent income.