After a preliminary investigation, fire officials, members of the Freeport Building Department and the county's hazardous materials team determined that the deadly gas came from hanging gas-fired heaters in the building, McManus said.
Mark Stuparich, an assistant chief for the Freeport Fire Department, said it was unlikely the building was equipped with a carbon-monoxide detector. "The thing would have been going off all morning," he said. Assistant Chief Stuparich said readings of indoor air showed upward of 500 parts per million (ppm) of carbon monoxide. According to the Environmental Protection Agency (EPA), normal indoor levels are 5 ppm or less. According to the Occupational Safety and Health Administration, the permissible exposure limit is 50 parts per million or less in an eight-hour period.