Police say an oxygen regulator caused the explosion in the Norwalk Hospital emergency room Sunday night.
The oxygen regulator was being transported on a gurney, according to police.
The gurney was transporting a patient into the emergency room with two attendants at the time of the explosion, police said.
There are burn marks on the wall and ceiling as a result of the explosion.
Firefighters found a moderate dust condition from a dry-chemical extinguisher, but no smoke or fire.
Police said an EMT attendant from out of town was treated and released while another EMT attendant and the patient were uninjured.
The hospital made arrangements to have the area of the explosion cleaned and expected to be fully operational by the end of the night.
No other injuries have been reported as a result of the explosion.
Maple Street was closed to traffic but has since reopened.