BOSTON (CBS) – The Boston Fire Department evacuated a five-story rooming house after a mixture of cleaning supplies created a Level 3 Hazmat situation Friday afternoon.

The fire department said there were reports of “noxious fumes” on the third floor of a five-story rooming house on Washington Street.

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Boston EMS transported 11 firefighters, who got a whiff of the gas, and a civilian to the hospital for treatment of conditions relating to the fumes and the oppressive heat.

“I don’t know if it was ammonia – but a chemical smell – and my eyes were running,” said resident David Moore, who grabbed a bathrobe to wear as he was evacuated.

Firefighters entered the building with monitoring devices Friday afternoon to find the cause of the odor. It turned out that a mix of bleach and Murphy’s Oil Soap created a toxic chloride gas. Firefighters are investigating who mixed the chemicals.

The Boston Fire Department responded to a hazmat situation in the South End on Friday. (WBZ-TV)

According to Deputy Chief Robert Calobrisi, a Level 3 hazmat situation is akin to a 9-alarm fire. “It’s like all hands on deck, basically, for a chemical spill, odor, gas, liquid – anything like that, where we don’t know what we have.”

The case manager for the Pine Street Inn building, William Ayala, pulled the fire alarm. “It made me gag as well so that’s why we pulled the fire alarm,” he said.

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The alarms were followed by knocks on the door telling residents they had to get out.

“We had probably about a minute, this is it,” Moore explained.

Firefighters were checked out continuously. They were given blood pressure checks and plenty of water. The 11 who inhaled the gas and one other person had to be taken to the hospital for evaluation.

“They got a whiff and the masks went on right away after that and luckily they did because it could have been a lot worse,” Calobrisi explained.

Boston Fire tells WBZ this all could have started with a cleaning company who comes weekly.

The exact cause is still under investigation.

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The building was cleared and ventilated. Residents were allowed back into the building, which will be monitored to make sure it stays clear.