Exhaust emissions of CO and NO2 are generated in parking garages as part of normal operations. While normal air exchange ventilation may minimize concentration build up, excessive concentrations can pose a health hazard. Continuous fan operation can be used to reduce emissions concentration but this increases maintenance costs, decreases system life, and increases energy costs. Using a gas detection system provides control for ventilation fans as well as alarming if gas concentrations reach unsafe levels.
Carbon Monoxide Safety Limits and Standards
|OSHA||8-hour TWA: 50 ppm|
|NIOSH||8-hour PEL- TWA: 35 ppm|
|ACGIH||8-hour TLV – TWA: 25 ppm|
|International Mechanical Code section 404.1||Mechanical ventilation systems for enclosed public garages shall be automatically operated by means of carbon monoxide detectors applied in conjunction with nitrogen dioxide detectors.|
Typical Action and Alarm Levels for Monitoring System
|CO (35 ppm), NO2 (2.5 ppm)||Engage ventilation|
|CO (75 ppm), NO2 (2.8 ppm)||Additional ventilation|
|CO (100 ppm), NO2 (3 ppm)||Horn and strobe alarm|
The safety standards above are based on 8-hour time-weight averages. Using the recommended alarm actions ventilation occurs at the first measurement of 35ppm concentration of CO and provides a significant safety factor against the 8-hour average.