Proactive vs. reactive CO2 sensing for improved indoor health

Article By : Dale Wedel

With a proactive approach to adding CO2 measurements, healthcare facilities can realize demonstrated benefits before regulations take effect.

Harmful levels of hydrocarbons and carbon monoxide have been known to moderately or even severely impact health and well-being for many years. However, the impact of high levels of carbon dioxide (CO₂) in confined indoor spaces has only become a serious focus within the last two decades. Recent technology advancements to accurately and cost-effectively sense CO₂ allow developers to reactively or proactively address the negative aspects of unhealthy levels of CO₂.

A proactive response provides an improved environment in the timeliest manner for those who would otherwise be subjected to those high levels. The stakeholders range from companies that do not totally rely on net meetings to conduct their business, to air handling and filtration system suppliers to building designers and owners as well as those responsible for building maintenance. Rather than react to government regulations, industry leaders should take a proactive, leadership position.

Impact of excessive CO₂ levels

As a byproduct of respiration, CO₂ levels increase in indoor spaces with increased population density. At different concentration levels, CO₂ can adversely affect the human body. As shown in Figure 1, the impact ranges from complaints of drowsiness to harmful effects due to oxygen deprivation. In between, performance and the attention of occupants is seriously compromised.

Figure 1 CO₂ is a key parameter in indoor air quality, so for occupant comfort and well-being, CO₂ measurements matter. Source: Wisconsin Department of Health Sciences, Fisk et al

Several years ago, the United States Department of Labor’s Occupational Safety and Health Administration (OSHA) regulatory agency established a Permissible Exposure Limit (PEL) for CO₂ of 5,000 parts per million (ppm). Here, 0.5% CO₂ in air averaged over an 8-hour workday (time-weighted average or TWA). Also, the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) has recommended that concentrations of CO₂ be maintained below 1,000 ppm in classrooms and 800 ppm in offices for many years.

More recently, the California Building Standards Code (California Code of Regulations, Title 24) or simply CA Title 24 Legislation, requires conformance. While CO₂-based Demand Controlled Ventilation (DCV) was part of Title 24 since 1996, it became mandatory for certain high-density applications in 2005. As an airborne disease, COVID-19 has brought increased attention to air filtration and concentration of people in small spaces. However, many existing CO₂ sensors still do not meet current accuracy requirements for effective DCV implementations.

Based on photoacoustic spectroscopy (PAS) technology, Infineon’s XENSIV PAS CO₂ sensor provides the performance—±30 ppm ±3 percent of reading—to meet Title 24 in a small form factor of 14 mm x 13.8 mm x 7.5 mm. With plug-and-play capabilities, the CO₂ sensor sets an affordable new standard for many high-volume applications.

Wellness is a key aspect of life and the places with the highest focus on wellness are hospitals or healthcare facilities. If they are not currently looking into how high, unhealthy CO₂ levels impact their patients, wellness providers from hospitals to clinics to treatments centers and researchers for these areas should review the findings of researchers (some from over 20 years ago) into how unhealthy CO₂ levels generally impact healthy individuals.

As part of their treatment, hospitals and healthcare facilities of all types should consider taking the next step in their treatments and healthcare protocols to ensure that the environment is most conducive to their patients’ recovery. An acceptable CO₂ level also enables optimum cognitive processes for healthcare providers. Since the patients are not at their normal level to fight infections, they do not need additional stress to their body from unhealthy air and, a speedier recovery could result from a healthier environment. This is even true for patients who are recovering at home.

Implementing CO₂ monitoring in critical locations

In its Munich headquarters, Infineon has taken a leadership role and installed CO₂ sensors in every conference room. The CO₂ concentration measurements are effectively a people counting technique. The readings indicate if too many people for the circulation and filtration system’s capabilities are present in a confined space.

Figure 2 Meeting rooms are equipped with CO₂ monitoring boxes to manage air quality and reduce the risk of COVID and other airborne virus transmission. Source: Infineon

With this data, appropriate actions can be taken, including something as simple as opening a window (Figure 3). Ultimately, a sophisticated system design with CO₂ sensors could automatically take a variety of actions to improve the situation and avoid problems for the attendees. Even a simple, red light/green light detection system can provide the warning for meeting organizers and attendees to take the appropriate action to avoid a health threat.

Figure 3 XENSIV PAS CO₂ non-compensated readout is consistent with reference meter for monitoring the meeting room CO₂ level in Munich. Source: Infineon

While meeting attendees have long used their own internal sensing—with each person reacting with their own individual response mechanism—to determine when a congested space becomes unhealthy, or stuffy as it is frequently called, the unbiased input from a CO₂ sensor can alert all attendees of the need to respond appropriately before individuals in the room start to experience discomfort and performance deterioration. Ultimately, in smart homes and smart buildings, this type of proactive response should eventually become a feature that distinguishes an advanced system from an average heating, ventilation and air conditioning (HVAC) system exchanging air based not only on temperature but other environmental factors, including CO₂.

As a sponsor for the Munich security conference, Infineon provided CO₂ monitoring for the conference with red light/green light levels in rooms. At this particular event, there were no red lights, so no actions were required. However, the next event could be totally different, since circumstances change at each one.

Let’s clear the air

With a proactive approach to adding CO₂ measurements to a facility, industry leaders, especially healthcare facilities, can realize many demonstrated benefits before regulations take effect. Infineon takes proactivity very seriously and has taken the first step in its own facility and encourages other stakeholders to take the first step toward improving the air quality in their facilities—prior to it being required. Certainly, those who can anticipate requirements similar to CA Title 24 spreading across the United States or other regional-specific requirements being implemented around the globe should be among the first to add CO₂ measurements to their control system and take their own first step toward cleaner, healthier air.

This article was originally published on EDN.

Dale Wedel is marketing manager for MEMS sensors at Infineon Technologies.

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