Customer A has an enclosed car park underneath their office block. Traditionally they have set the ventilation fans to come on at 07:00 AM until 10:00 AM, 11:30 AM until 14:30 PM and 16:00 PM until 19:00 PM. This provided the adequate number of air changes required when the car park was at its most busy but didn't allow for any change in work patterns and was running the fans when they were not needed just in case.
A survey was carried out of the site and the appropriate amount of Carbon Monoxide and Nitrogen Dioxide alarm sensors were installed to the car park and entrance roadway.
Once the gas levels have started to build up to 30ppm CO or 3ppm NO2 the ventilation fans operate to clear the toxic fumes, if the levels should continue to rise (this would normally only happen if the fans fail) sounders and beacons operate to let people know to vacate the area.
This has proved a very cost effective solution to the Customer who has seen a vast reduction in cost of running the ventilation fans when they are not required and they also know that they are giving adequate cover to staff under their duty of care.
Carbon Monoxide (CO) is the main component of vehicle exhaust emissions from petrol engines and Nitrogen Dioxide (NO2) is the main component of vehicle exhaust emissions from diesel engines. CO and NO2 are toxic and a health risk to the general public or employees who operate below ground or enclosed car parks.
This hazard is also present in below ground/enclosed road service tunnels used to deliver goods to shopping centres and engine test facilities.
A variety of organisations have published recommendations for the design of mechanical ventilation used to reduce or remove the risk of Carbon Monoxide levels and Nitrogen Dioxide alarms. At the core of these recommendations, is the need to achieve an adequate number of air changes per hour. Whilst this approach is effective, the associated running costs of mechanical ventilation (in Kilowatt hours) often proves expensive. An acceptable alternative approach is to monitor CO & NO2 levels and activate/ regulate the mechanical ventilation to ensure CO & NO2 levels are within acceptable limits and therefore reduce ventilation running costs.
A car park gas detection system consists of a number of strategically located sensors hard wired to a control panel. Upon the detection of gas, alarm relay contacts within the control panel are activated. These relay contacts can be used to operate warning signs (‘Switch off engines’, ‘Evacuate car park’) and initiate increased levels of mechanical ventilation via the ventilation control panel or a Building Management System (BMS).
Gas sensors are often located above or near to:
• Vehicle road ways
• Pedestrian entrances
• Exits and ramps
• Attendant pay booths
Consideration must be paid to the mechanical ventilation and its likely effect upon the path of CO & NO2 when locating a gas sensor.
Location of Control Equipment:
Gas detection control panels for car park applications are often located within the ventilation plant room, or in sight of the attendant/ supervisor.
Car Park Gas Detection - Case Study