CO2 and Ventilation

Mike Schell, the company’s director of marketing, has written about the subject of demand-controlled ventilation (DCV) for technical and engineering journals. The idea behind DCV is that by measuring the amount of CO2 breathed into the air, a building ventilation system can deliver the amount of ventilation that is really needed.

Currently, most ventilation systems work at a fixed rate. By using a CO2 monitor, a more accurate reading can be obtained. A wall-mounted CO2 monitor is wired to the building’s ventilation system. This system then reads the level of CO2 throughout the day.

For example, when there aren’t many occupants in a building, the CO2 level will be low. This will trigger the ventilation system to provide a lower level of ventilation. The opposite is then true when there is a large number of people present in the building.

The idea seems to be catching on. Purdue University recently installed CO2 sensors in six of its larger lecture halls. The Harley-Davidson Motor Company did the same thing, installing sensors at its corporate headquarters in Milwaukee, WI.

“The principle is that all people will breathe out a certain amount of carbon dioxide,” said Schell. “When we go into a building, we can determine the amount of ventilation needed per person.” By using a CO2 monitor, the building ventilation system can run on real-time occupancy. Instead of running at a fixed rate, a ventilation system that runs due to the amount of CO2 in the air will be running at different levels throughout the day. When the CO2 levels are low, less ventilation will be needed and hence less energy will be used.

New Products

Besides wall-mounted monitors, Telaire has several instruments and tools used to detect CO2 levels.

The Telaire 7001, a portable CO2 and temperature monitor, has been on the market for three years. It can run for more than 70 hrs on four AA alkaline batteries or continuously with a power adapter.

The handheld monitor comes in handy when determining if a particular building has adequate ventilation. The device can record its readings to be displayed later. “We can use it to determine if the building is appropriately ventilated. We can see if it is under or over ventilated,” said Schell.

The company also introduced a product that complements the 7001 as well as a majority of its other products. The CO2 View is a software logging program compatible with Windows. Both the CO2 View and the 7001 are used to determine if a building could benefit from CO2 sensors like those used at Purdue University. The program, when used with one of the company’s monitors, can graph the CO2 levels over a period time.

According to Schell, all of its monitors have an RJ45 telephone jack. A cord is plugged into this jack and connected to a PC. After the PC is hooked up to the monitoring device, it can begin graphing levels of CO2.

“It’s like an EKG of the building,” said Schell, adding that the program can be set to record the carbon dioxide level over any amount of time. It can record the level every five minutes or every 30 seconds, depending on the desired reading.

Publication date: 03/08/2001