Madison, WI – A carbon monoxide leak on a boiler at a Downtown hotel sent two people to the hospital Saturday night.

The incident happened at about 8:50 p.m. Saturday at the Doubletree Hotel, 525 W. Johnson St., the Madison Fire Department said.

The two people were part of a group of 8 to 10 people who had been using the pool and hot tub of the hotel.

“The family said they just spent an hour in the pool and hot tub, and after two of their relatives passed out, they called 911,” said MFD spokeswoman Cynthia Schuster.

The family was in a stairwell near the pool when two people passed out.

“Air monitors showed carbon monoxide readings of 150 parts per million in the stairwell, so everyone was told to evacuate while firefighters stepped outside to put on their breathing apparatus,” Schuster said.

Carbon monoxide readings went up to 400 ppm in the pool area, and readings peaked at 2,000 to 2,500 ppm in the boiler room.

“Firefighters opened multiple doors to begin ventilating, and Madison Gas and Electric was called to help identify the source,” Schuster said. “MGE determined an exhaust pipe on one of the boilers had fallen off and was discharging exhaust into the room.”

The air was cleared in the boiler room and pool area and adjacent hotel rooms and other floors were checked for elevated levels of CO. No other hotel guests complained of illness.