Demand controlled ventilation
Demand Controlled Ventilation (DCV) is an automatic adjustment of ventilation equipment according to occupant choice. DCV is a control method that modulates the volume exchange of fresh or outside air into an enclosed space by mechanical air conditioning equipment. Design engineers reference a codified standard when determining ventilation set points in order for sensors or time schedules and control loops to achieve indoor air quality.
There is a significant energy saving potential in rigorous outdoor air control.
Common reference standards for ventilation:
- ISO ICS 91.140.30: Ventilation and air-conditioning systems
- ASHRAE 62.1 & 62.2: The standards for Ventilation and Indoor Air Quality
Examples of estimating occupancy
- Timed schedules
- Motion sensors (various technologies including: Audible sound, inaudible sound, infrared)
- Gas detection (CO2) In a survey on Norwegian schools, using CO2 sensors for DCV was found to reduce energy consumption by 62% when compared with a constant air volume (CAV) ventilation system.
- Positive control gates
- Ticket sales
- Security equipment data share (including people counting video software)
- Inference from other system sensors/equipment, like smart meters 
Carbon Dioxide Sensing
Carbon dioxide sensors monitor carbon dioxide levels in a space by strategic placement. The placement of the sensors should be able to provide an accurate representation of the space, usually placed in a return duct or on the wall. As the sensor reads the increasing amount of carbon dioxide levels in a space, the ventilation increases to dilute the levels. When the space is unoccupied, the sensor reads normal levels, and continues to supply the unoccupied rate for airflow. The amount of air supplied is determined by the building owner standards, along with the designer and ASHRAE Standard 62.1.  Carbon dioxide sensors provide a way to provide accurate ventilation for the determined occupany and improve the carbon dioxide concentration of the space. The sensors allow for an accurate reading of the space, allowing building owners to save money on building operation costs.
- KMC Controls. (2013). Demand Control Ventilation Benefits for Your Building. Retrieved 25 March 2013, from http://www.kmccontrols.com/docs/DCV_Benefits_White_Paper_KMC_RevB.pdf
- Mysen, M., Berntsen, S., Nafstad, P. & Schild, P. G. (2005). Occupancy Density and Benefits of Demand-controlled Ventilation in Norwegian Primary Schools. Energy and Buildings, 37(12), 1234–1240. Retrieved October 9, 2012.
- Jin, M.; Bekiaris-Liberis, N.; Weekly, K.; Spanos, C. J.; Bayen, A. M. (2017). "Occupancy Detection via Environmental Sensing". IEEE Transactions on Automation Science and Engineering. PP (99): 1–13. doi:10.1109/tase.2016.2619720. ISSN 1545-5955.
- University of California, Merced. "Occupancy Measurement, Modeling and Prediction for Energy Efficient Buildings". Retrieved 26 March 2013.
- Lawrence Berkeley National Laboratory. "Carbon Dioxide Measurement & People Counting for Demand Controlled Ventilation". Retrieved 26 March 2013.
- Jin, M.; Jia, R.; Spanos, C. (2017). "Virtual Occupancy Sensing: Using Smart Meters to Indicate Your Presence". IEEE Transactions on Mobile Computing. PP (99): 1–1. doi:10.1109/tmc.2017.2684806. ISSN 1536-1233.
- Lin, X., & Lau, J., P.H.D. (2016). Applying demand-controlled ventilation. ASHRAE Journal, 58(1), 30-32, 34, 36. Retrieved from https://search.proquest.com/docview/1755482305?accountid=9445