The impact occurred in a third floor property in Chippenham’s Market Place soon after 18:00 BST.
A cordon is set up and close-by structures have been emptied, Wiltshire Police said.
Dorset and Wiltshire Fire and Rescue Service said the property had endured “noteworthy auxiliary harm”. The reason for the blast isn’t yet known and an examination is under way.
The man was taken to Southmead Hospital in Bristol however later exchanged to a pro consumes healing center in Swansea.
Volunteers from the British Red Cross are supporting those influenced and brief overnight convenience is being orchestrated a few inhabitants.
Supt Phil Staynings said the examination was in the “beginning periods”.
“We are working with the fire and protect administration and Wiltshire Council to secure the property, which has managed noteworthy basic harm,” he said.
“At this stage, we can’t decide the reason for the blast however our examination will proceed for the duration of the night.
“We might want to thank nearby organizations who have given refreshments, haven and convenience amid the night and in addition volunteers from the British Red Cross who are supporting anybody influenced.”
The cordon keeps running between St Mary Street, Market Place and Timber Street.