A longtime employee of MedStar Washington Hospital Center died Sunday after being overcome by fumes of a gas used in air conditioning equipment. As many as four other people were treated after the leak of what was described as Freon gas.

Freon, a synthetic refrigerant used in air conditioning equipment, can cause asphyxiation in confined spaces.

The employee, identified as Melvin Lewis, was overcome in a mechanical room near the auditorium in the hospital center’s east building, said center spokeswoman So Young Pak.

She said he had gone there in response to a request to fix the air conditioning.

After being overcome, she said, he and a colleague were taken immediately to the hospital’s emergency department, where Lewis died. The colleague was expected to be released after observation, she said.

A spokesman for the D.C. fire and emergency services department said firefighters were sent to the hospital center about 2:30 p.m. after a freon leak was reported. The spokesman, Timothy J. Wilson, said five people were taken to the emergency room.

The hospital spokeswoman said the building where the leak occurred was an annex that houses mostly offices and a small number of patients. Some of them were evacuated for a time, she said.

She said the air conditioning system in question apparently does not supply the main hospital building at the center.

She also said that it appeared that an air conditioning chemical was involved, but that she could not confirm that it was Freon.

The spokeswoman said Lewis, who had worked at the hospital for 15 years, was well known there and was remembered for his loyalty, dedication and ready smile. His age and address were not available immediately.

She said the matter is under investigation.

Peter Hermann contributed to this report.