NDIR CO2 Sensors in Fresh Air Systems to Optimize Air Quality and Energy Efficiency

Why are NDIR CO2 Sensors So Important for Fresh Air Systems?

When working with demand control ventilation systems, it is essential to comply with ASHRAE standard 62.1 about Ventilation for Acceptable Indoor Air Quality, an industry benchmark offering guidelines for multiple building design and construction requirements, aiming to reduce energy consumption and improve indoor air quality (IAQ).

It is worth noting that in the field of indoor ventilation, ASHRAE standard 62.1 has recently published set stringent standards for Demand Control Ventilation (DCV) Systems as follows:

6.2.6.1.3.1 CO2 sensors shall be located in the space between 3 ft (0.9 m) and 6 ft (1.8 m) above the floor. There shall be at least one CO2 sensor per ventilation zone and at least one per 5,000 ft² (460 m2) of net occupiable floor area. Where DCV ventilation zones are comprised of more than one room, each room shall have a CO2 sensor and ventilation shall be controlled to the room requiring the most ventilation.

6.2.6.1.3.4 CO2 sensors shall be certified by the manufacturer to be accurate within ±75 ppm at concentrations of 600, 1000, and 2500 ppm when measured at sea level at 77°F (25°C). Sensors shall be factory calibrated and certified by the manufacturer to require calibration not more frequently than once every five years. Upon detection of sensor failure, the system shall provide a signal that resets the ventilation system to supply the required minimum quantity of outdoor air (Vbz) to the breathing zone for the design zone population (Pz).

Under this context, ASHRAE mandates the adoption of CO2 sensor in a DCV system, especially the precision requirement of ±75 ppm at concentrations of 600, 1000, and 2500 ppm, which has sparked widespread attention to CO2-based DCV implementation.

When it comes to DCV, the fresh air system will come first. A fresh air system is a system for indoor air treatment and ventilation, with the main function of introducing fresh air, discharging indoor dirty air, filtering and conditioning the air to provide good indoor air quality, and creating a comfortable environment.

To realize demand control ventilation, CO2 sensors are imperatively introduced into the ventilation system, where the fan speed of fresh air machine is able to be intelligently controlled based on CO2 sensor measurement to keep the indoor CO2 concentration under a certain level. By adopting CO2 sensors to continuously and accurately monitor indoor CO2 concentration levels in real-time, fresh air is supplied according to the real-time and exact demand. When it is detected that the indoor CO2 concentration exceeds the set threshold, the fresh air machine will automatically increase the air ventilation volume to bring fresh air into the room to reduce the CO2 concentration. When it is detected that the indoor CO2 concentration is within the normal range, the fresh air machine will correspondingly stop or reduce the fan operation, thereby saving energy. Through effectively transferring accurate data of indoor CO2 concentration, CO2 sensors in DCV systems can realize intelligent air ventilation control to maintain indoor air quality and improve energy efficiency at its best. Therefore, it is important to adopt highly accurate and fast response CO2 sensors for precise indoor air ventilation control in time.

As the leading manufacturer of CO2 sensors, Cubic has developed various kinds of CO2 sensor based on non-dispersive infrared (NDIR) technology with more than 20 years' dedication in the field. With matrix calibration technology within whole measurement and temperature range, Cubic CO2 sensors can work at wide range of conditions and keep stable performance with high accuracy of ±75 ppm at concentrations of 600, 1000, and 2500 ppm to meet the ASHRAE standard for the fresh air ventilation system, so as to optimize air quality and energy efficiency in modern buildings.