Effective July 1, 2019 in the City of Rockville and in Montgomery County, homes with any fuel burning appliance that has access to the interior air of the home, or an attached garage, requires that one or more Carbon Monoxide (CO) detectors be installed for occupant safety and protection.
The law passed by Montgomery County (and incorporated by the City of Rockville) as interpreted by the Montgomery County Fire & Rescue Services requires: If a fuel-burning appliance, fireplace, or attached garage is present, an interconnected battery back up carbon monoxide alarm or detector must be installed outside all sleeping areas and on all floors. If a fuel-burning appliance [i.e. space heater] or fireplace is present in any sleeping area, an interconnected carbon monoxide alarm or detector must also be installed in that room.
Note that the County & City laws are based on an earlier Maryland state law that also applies.
CO Detection Details and Statistics
Choosing a CO Alarm is not an easy task as the Set Point where the alarm will trigger can vary from one manufacturer to another. Selection of a Carbon Monoxide detector is not the same as selecting a smoke alarm, as CO can vary over time, like blood pressure, so knowing when the level starts to rise can notify you of a developing problem that can be addressed before the situation becomes dangerous to the health of occupants.
Available alarms have different alarm (limit) points, which when met will cause the alarm to trigger. This information is important to know, based on the systems in the home, the age and condition of the systems, the number, age, and condition of the occupants, and the tightness of the air envelope of the home.
Oxygen (O2) Concentrations: Low: 19.5%, High: 23.5%, Fresh air contains 20.9%. Any environment in which the concentration of oxygen is less than 19.5% has been determined by OSHA to be oxygen deficient.
CEIL - Ceiling Limit / Alarm STEL - Short Term Exposure Limit / Alarm TWA - Time Weighted Average / Alarm
OSHA Rule for CO Gas: Ceiling - CO 35 ppm TWA - CO 35 ppm STEL - CO 100 ppm