Interest in indoor air quality in public buildings such as offices, schools and other institutions has increased as the demand for lower energy consuming buildings has resulted in tighter building envelopes that reduce uncontrolled leakage of heated or cooled air. Tight buildings place a premium on the importance of ventilation. When air change rates and air filters are not adequate, the chance of health impacts on occupants increases.
Tight buildings can save energy. They can also cause higher levels of pollutants such as CO2, volatile organic compounds and particulates in the indoor air. While the HVAC system can provide controlled ventilation that includes outside air and filtration to mitigate the build-up of pollutants, few building operators actually monitor the pollutant levels to know if the ventilation and filtration systems are sufficient.
Indoor air spaces can be affected by a mix in both outdoor contaminants from traffic exhaust or pollutants generated by commercial or industrial operations, as well as contaminants from indoor sources including emissions from building materials, HVAC systems, electronic equipment and cleaning chemicals.
Occupant Health and Performance Effects
The health effects on the occupants of a space with poor indoor air quality vary by the predominance of a specific pollutant. However, in general, these effects include:
- irritation of eyes, nose and throat
- respiratory disease
According to the National Institute of Health (NIH), “Minimizing indoor air pollutants is paramount to high performance schools, due to the potentially detrimental effects that VOCs, particulate matter including allergens and molds, and combustion gases may have on the health and wellbeing of students. In addition to their capacity to trigger asthma or allergy attacks, some of these pollutants are notorious for causing flu-like symptoms, headaches, nausea, and irritation of the eyes, nose, and throat. Moreover, a recent research suggests that a school’s physical environment also can play a major role in academic performance.”
This assessment for schools applies to the workplace as well. Fatigue or headaches will affect productivity. Respiratory issues will increase absenteeism. In short, poor indoor air quality in the workplace has an impact on the bottom line.
Building operators can mitigate the effects of poor indoor air quality several ways. Adjusting the ventilation rates and the amount of outside air included in the ventilation may be appropriate when addressing specific contaminants such as CO2 or volatile organic compounds. They can also install better air filters in the HVAC system to address high particulate concentrations. However, any mitigation strategy requires an understanding of the specific contaminant that exists at elevated levels in the indoor environment and may be affecting the performance and productivity of the occupants.
Diagnostics with IAQ Sensors
Today, there are sophisticated air quality sensors available for commercial and institutional buildings. These sensors provide hourly data on CO2, VOCs, large and small particulates, humidity and ozone. The sensors often provide connections to the cloud for data reporting, dashboards for desktop analysis of the data and some are BACnet compatible for connection to existing building automation systems. Data can be exported and shared with other personnel.
Here are two screen shots from a Kaiterra Sensedge sensor dashboard that show examples of pollutant data for one office in a larger office building.
This 24 hour period snap shot, shows a graph of the overall air quality index. The numerical values above the graph show the average levels for each pollutant within this 24 hour period. The overall index is very good at "41" ("100" is unhealthy) with minor levels of the particulates. Both CO2 and total volatile organic compounds (TVOC) levels are in the healthy range but both are worth watching because the levels are not insignificant. By selecting the CO2 or TVOC tabs just below the graph, you can view the graph of each pollutant and see if within this period there are peaks that reach unhealthy levels. The second image below demonstrates this with TVOC.
The graph in this snap shot shows only TVOC levels throughout the period. Around 8:30am the TVOC level peaked at a level that is moderately unhealthy, then relatively quickly dropped down to a healthy level. A building operator can use both the graphs for individual pollutants and also the numerical averages over longer periods to discover any patterns of concern for particular pollutants.
Monitoring is the key to successful management of indoor air quality. Once the building operator identifies a consistently high level of a specific pollutant, appropriate mitigation strategies can be implement. The effectiveness of the mitigation can also be monitored and adjusted if necessary.
The tangible benefits of indoor air quality monitoring and mitigation - improved occupant performance, increased productivity, reduced absenteeism - provide a strong case for the value to businesses and schools as well as other institutions.
Today the concept of "healthy buildings" is becoming commonplace and includes many factors such as light, water quality, acoustic performance as well as indoor air quality. Certification programs now are available to provide benchmark performance metrics as well as recognition for healthy buildings. These programs are designed to motivate, guide and reward building operators who manage buildings that meet program standards: WELL, RESET, fitwel.