By Katie Brace

BOSTON (CBS) — As hot as it was outside Sunday, it was a lot worse for firefighters battling a house fire in Mattapan.

The firefighters have faced more challenging fires, but perhaps not such punishing heat. One was treated for heat issues; he was having difficulty breathing due to the weather.

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The temperature was 93 and the heat index 100. Firefighters suited up in their heavy gear and faced the burned flames on Alabama Street.

“It increases the ability of people to have heat stress rather quickly,” said Boston Deputy Fire Chief Andre Stallworth.  “Their normal working times are greatly reduced and we have to replenish them and swap them out more quickly than we like.”

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The heat forced Boston fire to call in extra crews.

Firefigthers said the fire started in a bedroom. The flames went out the window spreading to the above floor and melting the siding of the neighboring house. The damage is estimated at $150,000.

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The injured firefighter is expected to be ok.