GREAT BARRINGTON — Carbon monoxide from a rotted-out furnace part sent five people to the hospital Sunday and rendered the building uninhabitable until repairs are made.

The patients are listed in stable condition, according to town Fire Chief Charles Burger.

At about 1 p.m. the town Fire Department got a call from Fairview Hospital, reporting that it had admitted three patients showing signs of carbon monoxide poisoning, Burger said in a statement.

The call prompted first responders to go to the building, where firefighters found high levels of carbon monoxide outside the front door, and no working smoke or carbon monoxide detectors inside, according to Burger.

The building's three floors were immediately evacuated, he said, noting that the building has a business on the first floor, and four apartments on the second and third floors.

Burger said carbon monoxide detection alarms are lifesavers.

"You can't see it, smell it or anything, so without detection there's really no way to know," he told The Eagle.

He said the culprit was the back of the furnace, "which had rotted off so the stove pipe was just venting straight into the basement."

After a carbon monoxide reading of 1,000 parts per million in the basement, and levels over 200 PPM throughout the rest of the building, the furnace was shut off and the entire building ventilated.

Burger said his detection meters peak at 1,000 PPM.

"So who knows how high it really was."

He said with one hour of exposure at 1,000 PPM, a person loses consciousness. "At 200 PPM, you'd start to experience some symptoms after an hour," he added.

According to the Centers for Disease Control, 400 people die annually from carbon monoxide poisoning.

The building, which is home to a yarn and gift shop, Wonderful Things, has been posted uninhabitable by the town Board of Health until multiple repairs are made and detection alarms installed.

Harry Sano, who said he owns the store and the building, told The Eagle that all of his tenants are living elsewhere in the meantime, and that they are all "fine."

But it was a close call, and Burger said it's best not to gamble with carbon monoxide.

"I cannot stress enough the importance of functioning smoke and carbon monoxide detectors — they save lives. This could have had a very different outcome had the incident occurred at night while everyone was sleeping, and I'm thankful that everyone will be OK."

He said it is important to change the batteries in detectors and call the Fire Department for help with that if necessary.

Heather Bellow can be reached at 413-329-6871, or @BE_heatherbellow