Posted: 8/23/21

Modern office spaces

How DCV Improves Your IAQ With A CO2 Sensor

As new buildings continue to pop up around the world, global demand for HVAC equipment meeting industry standards will continue to rise. These new buildings (and even existing buildings now) strive to meet proper design requirements for things like increased energy efficiencies and occupant comfort. Ventilation standards (such as the ANSI/ASHRAE 62.1-2007) in these buildings help specify minimum rates and other measures intended to provide acceptable levels of indoor air quality (IAQ) to human occupants and minimize adverse health effects.

While still ensuring the standards are met, contractors implement Demand Control Ventilation (DCV) systems. Demand-controlled ventilation using CO2 sensing is a combination of two technologies: CO2 sensors that monitor CO2 levels in the air inside a building, and air-handling systems that use data from the sensors to regulate ventilation. CO2 sensors continually monitor the air in a conditioned space. Since people exhale CO2 the difference between the indoor CO2 concentration and the level outside the building indicates the occupancy and/or activity level in a space and thus its ventilation requirements. The sensors send CO2 readings to the ventilation controls, which automatically increase ventilation when CO2 concentrations in a zone rise above a specific level.

By monitoring the levels of CO2 based on the number of people in the space, DCVs help occupants from becoming dizzy, fatigued, or nauseous, while also lowering energy costs by not constantly having to run your system.

Either too little or too much fresh air in a building can be a problem. Over-ventilation results in higher energy usage and costs than necessary with appropriate ventilation and potentially increases IAQ problems in warm, humid climates. Under-ventilation leads to poor air quality which can cause occupant discomfort and health problems. The heating, ventilation, and air-conditioning system can use DCV to tailor the amount of ventilation air to the occupancy level.

Room diagram

The ACI advantage

The advantages of installing an ACI CO2 sensor that communicates to the Building Automation Systems instead of a stand-alone device are:

  • Improved IAQ—increasing the supply of fresh air to the space prevents poor IAQ due to high occupancy.
  • Energy savings—CO2 sensors as part of DCV will ventilate the space only when needed.
  • Improved humidity control—when paired with humidity sensors, DCV can ensure proper humidity levels which mitigate the spread of mold, mildew, bacteria, and viruses.
  • Data for building analytics—data can be logged and used with analytics software to maximize HVAC performance.
  • Compatible with nearly every HVAC control system—the measurement range of most CO2 sensors is 0-2000 parts per million (PPM). The sensors output an analog (0-10VDC or 4-20mA) or a digital (BACnet or Modbus) signal.
  • Occupant health and safety—research shows a strong correlation between CO2 levels and the airborne spread of viruses and bacteria.

    ASHRAE 62.1-2007 states that the differential between the indoor and outdoor CO2 levels should be 700 PPM, helping to meet the 15 CFM air flow rates per person.  These levels are set to reduce energy costs and unnecessary air treatments, so a CO2 sensor with a good range of PPM measurement is key in maintaining that standard.


    Another key component of a good CO2 sensor the ability to self-calibrate its own sensor. Software such as ABC Logic takes a continual 14-day average of the lowest CO2 levels in an area and self-calibrates the sensor off of that baseline. This ensures an accurate sensor without having to physically re-calibrate all of the time. It will also save you money by determining actual occupants in the room versus a fixed rate of CO2, helping your DCV successfully ventilate your area.


    Your CO2 sensors are at the front line of a functioning DCV system, so making sure you have the right one will improve your IAQ, minimize possible adverse health effects, and save you time and money.

We Want To Hear From You!

 Have Questions? Comments? Ideas for Topics? Let us know!