Major Alastair Macartney, 34, from Fairburn, near Castleford, competed against full-time professional sky divers in the competition near Moscow.
Although many people had left the area because of fire and smoke, Maj Macartney, the only British competitor, decided to stay.
He described fires that were burning all around the dropzone at Kolomna, south east of Moscow.
"The smoke often reduced visibility to about 30m and everyone was seeking refuge indoors despite the stifling heat.
"The fires came within a few hundred metres of the hotel the athletes were staying in. During the competition the fires started to spread to Chernobyl and there was a risk of radiation drifting across," he said.