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  • Sysinno Technology

Why is the TVOC in the conference room persistently high even when no one is present?


Recently, a customer reported that the TVOC levels in their conference room remained high during holidays, despite the absence of people in the room and the continuous operation of the ventilation system. Upon receiving this issue, our air quality analysis team at Sysinno immediately initiated an investigation. By utilizing precise data recorded by the iAeris sensor and examining the surrounding environmental conditions, we were able to uncover the root cause and provide a solution for the customer. TVOC, which stands for Total Volatile Organic Compounds, is one of the air quality factors regulated by the Environmental Protection Agency. TVOC pollution can originate from various sources, including indoor scents, essential oils, incense burning during rituals, various cleaning agents used during cleaning, cooking odors from the kitchen, and outdoor air pollution emissions from factories, automobiles, and more. All of these sources can lead to an increase in TVOC detection levels. The customer's conference room is equipped with a ventilation system, an iAeris air quality monitor, and a KR02 IoT controller. These installations not only provide real-time information about the air quality in the conference room but also enable the ventilation system to adjust its operation based on air quality. It was observed recently that during holidays when the conference room was unoccupied, TVOC levels would abnormally rise, which was a rare occurrence. We conducted an analysis of historical data from the iAeris monitor and found several key observations:

  1. Initially, we examined the correlation between TVOC and formaldehyde (HCHO) levels. On normal working days when the conference room was in use, alcohol-based disinfection was performed (alcohol is one of the components of TVOC), resulting in several daily TVOC peaks. Since alcohol can also affect formaldehyde sensor readings, changes in formaldehyde levels were directly related to TVOC fluctuations. However, during holidays when alcohol was not used, it was expected that TVOC and HCHO levels would not exhibit a strong correlation. As shown in Figure 1, the formaldehyde levels during holidays were close to zero, while TVOC levels showed some fluctuations. This indicates that there may be underlying air quality issues in the environment. Upon customer confirmation, it was established that during holidays, no one entered or exited the conference room, and there was no cleaning or disinfection activity taking place.

Figure 1: Indoor TVOC vs. Formaldehyde Comparison Chart


2. Regarding the unusual increase in TVOC levels in the conference room during holidays when no one is present, we began analyzing various potential factors. Since holidays involve only outside air intake with no personnel entering or exiting, we suspected that external environmental factors might be causing this phenomenon. After downloading monitoring data from the nearby Environmental Protection Agency (EPA) station located 4 km away and cross-referencing it, we found a correlation trend between indoor TVOC levels and EPA's NMHC (Non-Methane Hydrocarbons) levels, both on working days and holidays (as shown in Figure 2).


Figure 2: Indoor TVOC vs. EPA NMHC Comparison Chart



3. Based on the analysis above, we believe that the increase in TVOC levels is not only due to various indoor volatile pollutants but also a mix of outdoor pollution. Since the ventilation system operates 24/7, it continuously brings in polluted outdoor air, especially during holidays. Furthermore, we identified several potential reasons contributing to the rise in TVOC levels: 1. There is ongoing subway construction near the conference room (50m away), which involves emissions from heavy machinery during operation, potentially contributing to outdoor TVOC pollution.


2. On the evening before workdays resume (Sunday or the last day of a consecutive holiday), TVOC concentrations consistently begin to rise. The conference room is situated close to a highway (150m away), which happens to be a bottleneck for traffic congestion during these times, leading to emissions from idling vehicles. This is also likely a source of outdoor TVOC pollution.


Through the analysis provided above, it becomes clear that our breathing air is influenced by numerous pollution sources in our current environment. An accurate and reliable air quality monitor can play a crucial role in monitoring air quality and assisting us in taking the right steps to improve indoor air quality.


By utilizing the precise detection of TVOC and HCHO provided by the iAeris air quality monitor, we have identified potential pollution sources, resolved the customer's concerns, and recommended effective strategies for reducing indoor TVOC levels. This enables our colleagues to work in a healthy environment and helps businesses take a significant step





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