Firman attended Gresham 's School in Norfolk.
His motorsport career started in karting. In 1993 he won the McLaren Autosport BRDC Award. Some years after he won 1996 British Formula 3 Championship, Firman started in the 2003 season in Formula 1 for Jordan at 14 Grand Prix. His best finish was eighth place at the Grand Prix of Spain. He reached a championship point. After only one year, he left the Formula 1, as his contract was not renewed.
In the meantime, he drove for the team Honda Racing in the Japanese Super GT Championship. In the 2005/06 season he drove for A1 Team Ireland in the A1 Grand Prix.