Kip Harris is a retired firefighter and gas expert, who happens to be Virgil Tracy's idol. He assisted a very over-excited Virgil and his teasing younger brother Gordon when the Chaos Crew were stealing gas from a gas field. Virgil has a lot of admiration for Kip, having read many of his books and even got a action figure of him since childhood.
It appears that Kip knew Jeff at least quite well. He even remarked that Virgil is "quite a chip off the old block", indicating that Virgil resembles his father.
When it came to tackling the situation, the leaking gas erupted into a blazing inferno by the aftershock from the explosives from the Chaos Crew despite the fact that Gordon (using Thunderbird 4) got it beyond the exclusion zone; even Virgil using Thunderbird 2's fire retardant grenades wasn't enough to put out the fire. So, Kip had no option but to put the fire out the old-fashioned way - using dynamite with his own formula of nitroglycerin. However, this meant placing it right in the centre of the fire. Virgil suggested doing this job himself, however Kip insisted that he knew what he was doing, so he did despite the risks. At first, when there was an almighty explosion from the dynamite, Virgil was deeply concerned for his hero, but fortunately for him, Kip came out from the smoke all alive and well.
Unfortunately, much to the Tracy brothers' displeasure, Grandma Tracy took quite a shine to Kip Harris; she even suggesting to Virgil that the retired firefighter may be someday his new grandfather.