What is CO
Carbon Monoxide or CO is a byproduct of combustion which results when carbon bearing fuels burn incompletely. CO is commonly associated with the use of fossil fuels. CO is dangerous because it binds more easily than oxygen to red blood cells and it is odorless. The effect on people varies depending on age, overall health and the concentration and length of exposure.
Understanding CO Levels
The OSHA recommended exposure limit (REL) for carbon monoxide is 35 ppm (35000ppb) as an 8-hour time weighted average (TWA). The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm TWA. This lower limit was established because of the danger of accumulation of CO in blood hemoglobin in some people. CO levels are important to monitor because the CO limits established by the EPA and OSHA are lower than the level needed to trigger CO alarms. CO alarms are tested to UL standard 2034 which specifies a level of 70ppm or higher to trigger an alarm. In addition, effective monitoring is crucial to identify potential sources before they become a problem. Note: CO alarms are required by law, monitoring is not a substitute.
Causes of High CO
Vehicle traffic in urban areas from outside air
Unvented kerosene and gas space heaters
Leaking chimneys and furnaces
Back-drafting from furnaces, gas water heaters, wood stoves and fireplaces
Gas stoves.
Generators and other gasoline powered equipment
Exhaust from attached garages
Worn or poorly adjusted and maintained combustion devices (e.g., boilers, furnaces)
A flue which is improperly sized, blocked, disconnected, or leaking
Resolving High CO Levels
A flue which is improperly sized, blocked, disconnected, or leaking
Increase outside air if CO levels are elevated from indoor sources
Monitor CO levels near combustion equipment
Make sure that negative-pressure HVAC conditions cannot occur in spaces where combustion equipment is located
Inspect and maintain flues and exhaust equipment
Measuring CO2
The most accurate way of sensing CO currently available is an Electro-Chemical (EC) sensor. This type of sensor detects a change of resistance in a chemically active layer between two electrodes. The WellStat devices have the ability to compensate for changes in both offset and slope of the sensor response.