Indoor air quality is critically important for building operators and occupants alike, but cost-effectively maintaining optimal air quality can be a challenge. This article explores the importance of carbon dioxide (CO2) measurement for optimizing indoor air quality and energy-efficient ventilation – and how accurate, high-quality CO2 sensors can contribute to a healthier, more productive indoor environment for us all.  

The importance of indoor air quality

The impact of indoor air quality extends far beyond comfort. Many common pollutants enter into and are generated inside buildings, especially in industrial areas. These pollutants can have both short and long-term health effects, including fatigue, headaches, asthma, and even heart disease and cancer.

Managing the air quality inside a building is essential to help mitigate these negative effects. Studies by the Continental Automated Buildings Association, the Federation of European HVAC Associations, the US Green Building Council, and the Carnegie Mellon University have all shown a connection between improved ventilation and improved business and educational outcomes.

There is also an economic argument: a study published in the Journal of Environmental Research and Public Health with contributions from the Harvard Chan School of Public Health has estimated that a mere $40 per person investment in HVAC improvements could yield an 8% increase in productivity. An accurate ventilation system can also deliver energy savings – making the money saving argument even stronger.

Optimizing ventilation with CO2 monitoring

While many different parameters contribute to indoor air quality, CO2 measurement offers some unique advantages as an air quality indicator. As a natural byproduct of human respiration, CO2 serves as a reliable marker for occupancy and other bio-effluents, offering real-time insight into ventilation levels.

CO2 is most commonly used as a measurement parameter in demand-controlled ventilation (DCV) systems. DCV is part of a building’s automation system and controls ventilation based on sensor data. The goal of DCV is two-fold:

• to increase energy efficiency by reducing the amount of outside air introduced when a space is unoccupied, and 
• to maintain a healthy indoor environment by bringing in sufficient air when the building is occupied.

By basing air supply on actual occupancy rather than fixed schedules, this intelligent approach to building ventilation delivers substantial energy savings while maintaining optimal air quality.

There have been multiple studies on the effectiveness of energy savings from DCV. For example, the U.S. Department of Energy has identified DCV as a primary contributor to HVAC energy savings in various commercial settings – particularly noteworthy given that HVAC systems account for approximately 40% of the energy consumption of commercial buildings. Importantly, research shows that the more accurate the carbon dioxide sensors, the more efficient the DCV system.

Are all CO2 sensors the same?

We’ve seen that an optimized ventilation system can improve health and productivity and reduce energy use, and that to optimize a DCV system you need accurate CO2 sensors. It’s important at this point to recognize that not all sensors on the market are the same.

To measure CO2 accurately you need high-quality sensors, otherwise the measurement will drift over time and you won’t get accurate results. Low-cost sensors don’t have a reference measurement and instead use a method called automatic background calibration. This approach uses a software algorithm in place of a true reference measurement to combat drift.

As well as being a correction factor based on an assumed value, automatic background calibration has other issues as well. It relies on the assumption that the lowest value of CO2 is periodically recorded. This value is assumed to be 400 parts per million – the average atmospheric CO2 concentration globally from several years ago. Unfortunately, this method is really only applicable in buildings with very consistent ventilation rates and very predictable occupancy, and not at all for buildings occupied 24/7. As a result, the accuracy of standard CO2 sensors relying on automatic calibration can be compromised, leading to inefficient ventilation and poor indoor air quality.

Superior performance with Vaisala Carbocap technology

If you’re looking for the most accurate and stable CO2 sensors on the market, those that use Vaisala Carbocap technology are unparalleled, and offer several unique advantages.

Key features include:

• Built-in reference measurements based on proprietary infrared filters, ensuring exceptional accuracy and long-term stability
• Temperature and barometric pressure compensation for reliable readings in both indoor and outdoor environments
• Microglow light source technology that reduces energy consumption while extending sensor lifetime beyond 15 years
• Lower self-heating, protecting neighboring sensors like humidity and temperature from a common source of error
• Protective shielding that maintains accuracy and stability even in challenging conditions with high humidity or dust

Vaisala Carbocap sensors are a precision solution that can also contribute to smart building automation by supporting digital twin technology, where real-time CO2 data helps to create accurate simulations of building performance. These sophisticated systems can predict airflow patterns, identify areas of concern, and suggest improvements before physical modifications are made.

It’s important to remember that even the very best sensors will require periodic calibration, and Vaisala are experts here too, with a full range of calibration services available. Vaisala also publish complete accuracy and performance specs – which is not something you'll find from many other manufacturers.

Building a healthier, more sustainable future

There is now incontrovertible evidence linking carbon dioxide, indoor air quality, productivity, and well-being. While there are a variety of parameters used to evaluate air quality and ventilation in a building, there’s no other real-time continuous monitoring solution that's as proven and reliable as CO2 measurement.

As we continue to spend more time indoors and face growing environmental challenges, the ability to maintain healthy indoor environments while minimizing energy consumption becomes increasingly critical. Accurate CO2 measurement, supported by advanced sensor technology, provides the data necessary to achieve this balance. By investing in reliable measurement solutions, building operators can create healthier, more productive spaces while meeting sustainability goals – a winning combination for both occupants and operators.

Vaisala has over 80 years of experience in environmental measurement and is trusted by the world’s leading authorities. Contact us today to find out how our sensors could improve your IAQ and benefit you.