A little before noon today, Katonah Fire Department was dispatched to a "residential fire alarm" on Mustato Road. Engine 115 responded along with Car 2211. Upon arrival, 2211 reported workers on the scene. When 115 arrived, its crew went inside the house to investigate the cause of the alarm. Almost immediately, the crew's four-gas detector went off, indicating dangerous levels of carbon monoxide (CO) inside. The crew took additional readings throughout the house, levels of over 140 parts per million of CO were discovered. Ventilation fans from 115, Rescue 17 and Ladder 39 were brought in to bring the CO levels down. BHFD was requested to the scene for additional ventilation equipment but their units were canceled enroute. As a precaution, Westchester Emergency Medical Services and Katonah-Bedford HIlls Volunteer Ambulance Corps were dispatched to the scene. After further investigation, and after verifying that the CO levels were down to zero, it was determined that a saw used to cut concrete resulted in the elevated levels of CO. Fortunately, the workers had evacuated the house before the CO could affect them. KFD and EMS units were operating at the scene for a little over an hour. As colder weather arrives and people spend more time indoors, Katonah Fire Department urges you to NEVER ignore or dismiss an alarm or chirping detector. It could be telling you something vital and it WILL save your life. This is also another reason that we stress the importance that we come in to your home to check for your safety.