Chicago, IL – Chicago fire officials are warning residents about using power-washers indoors after they were called to a South Side home Tuesday morning when fumes from a gasoline-powered washer led to elevated carbon monoxide levels.

The Chicago Fire Department called for a HazMat response about 10:15 a.m. for high levels of carbon monoxide at a building in the 8000 block of South Champlain Avenue.

The CO level reached 1,000 parts per million, a level that is potentially deadly, according to Fire Media Affairs. The high levels were caused by the use of a power-washer in a basement.

Though no injuries were reported, Fire Department officials stressed that the CO levels reached were “deadly and will kill in minutes.” The department urges residents to “never use gasoline-powered machines inside, even with doors open. Always keep units outdoors.”

The building had CO detectors and 911 was called “before it was too late,” according to Fire Media.