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Indoor air quality

03/03/2022 Yves Vinck

The purpose of ventilation is to supply fresh outside air and extract stale air and pollutants from inside. The supply of fresh air can be seen as the first step towards good indoor air quality. However, a ventilation system is not a guarantee for good indoor air quality. In this article, we discuss some important points to consider.

Indoor air quality
Indoor air quality and our health

Most people spent the majority of their time indoors. That’s why indoor air quality has a direct impact on our health and general well-being. International studies have shown that the levels of indoor air pollutants are typically 2 to 5 times higher than outdoor levels. The purpose of ventilation is to supply fresh outside air and extract stale air and pollutants from inside. The supply of fresh air can be seen as the first step towards good indoor air quality. However, a ventilation system is not a guarantee for good indoor air quality. Is the supply of fresh air sufficient? Is stale air extracted sufficiently? Was maintenance performed regularly and correctly? In addition to improving indoor air quality, a ventilation system also helps to reduce the risk of transmission of COVID-19 and other viruses via aerosols. To reduce the risk of spreading COVID-19, it is best to limit recirculation of indoor air as much as possible. 

Is there sufficient fresh air supply?
The required amount of fresh air supply depends on many factors. Sometimes the necessary supply of fresh air is calculated based on the volume of the room. In this scenario, varying room occupancy rates are not taken into account. Sometimes there will be too much ventilation, sometimes too little. The number of people in a given space is one of the most important factors in determining the minimum required fresh air supply. People exhale CO2. Moderate to high levels of carbon dioxide can cause headaches, concentration problems and fatigue. Fresh air supply reduces the CO2 level inside a room. The more occupants, the more fresh air is required. That’s why many ventilation systems are controlled by a CO2 sensor. In this way, the fresh air supply is always optimal.
Another important factor are the sources of VOC or Volatile Organic Compounds. These kind of pollutants origin from paint, cleaning products, aerosol sprays, disinfectants, etc. VOCs have a negative impact on our health. A ventilation system supplies fresh air into the building and extracts stale air and VOCs from the building. VOC or air quality sensors detect these contaminants and can further optimize the control of the ventilation system.
Too much ventilation is not bad in itself, but the faster a fan runs, the more energy it consumes and the more noise it generates. Too much ventilation means excessive energy consumption and extra noise. CO2 and VOC sensors automatically vary fresh air supply based on the demand. They control the ventilation system to guarantee a good indoor air quality and to increase the comfort of the inhabitants.
Fresh air supply is the basic principle of ventilation and the first step towards good indoor air quality. In addition, there are a few other important points to note.
Filters and filter maintenance
Most ventilation systems are equipped with air filters to protect the fans and to remove pollutants in the form of particles from the air. Over time, the air filters of the ventilation system become saturated. Saturated or clogged filters work less effectively and will stop fewer particles. It is important to schedule preventive maintenance and clean or replace these filters at regular intervals. Supplying fresh outside air through filters that are heavily contaminated with pollen, dust and fungi is detrimental to healthy indoor air quality. Dirty filters also offer more resistance to the airflow. This will translate into additional energy consumption.
It is therefore recommended to monitor each filter with a differential pressure sensor. For Air Handling Units or installations with multiple filters, we designed HPD and DPD sensors. One of these sensors can monitor the differential pressure in two different locations. When the filter becomes saturated, the differential pressure will increase. When a threshold is exceeded, it is time to replace the filter. If necessary, an alert can be sent to the installer or to the maintenance provider. It is also possible to log the measured values online. This makes it easier to schedule maintenance.
Air purifiers
COVID-19 has had a significant impact on the demand and interest for air purification systems. UV light can help provide an additional layer of defense against viruses, bacteria, and microbes. UV Air purifiers use ultraviolet light to destroy biological impurities such as viruses, molds and bacteria. The effectiveness of these systems depends on the exposure time. Some viruses and bacteria need to be exposed to UV light during one or more hours before they become completely harmless. An air flow passing through UV light during a few seconds, is not always a guarantee to completely remove these microbial pollutants. That's why air purifiers are usually added to the ventilation system to additionally purify the (already filtered) air.
Humidifiers and dehumidifiers
Temperature and relative humidity have a direct impact on the sense of well-being and comfort of the residents. For that reason, most Sentera sensors monitor temperature and relative humidity. Dry air leads to dry skin, itchy eyes, and irritated nasal passages. A humidifier increases the relative humidity by boiling water into steam or by vibrating water droplets into the air with ultrasonic technology.
Too high relative humidity degrees will result in condensation forming on windows, walls and ceilings that are colder than the air temperature and potentially damaging building materials and causing odors in poorly ventilated spaces. A dehumidifier reduces the relative humidity. Dehumidifiers bring the airflow in contact with a very cold coil. Due to the low temperature, condensation occurs and relative humidity decreases. Sentera duct sensors monitor temperature and relative humidity in the air ducts and provide the required information to control an electric duct heater, a humidifier and / or dehumidifier.
Monitor indoor air quality
Just like a complete Sentera HVAC control solution, also a stand-alone HVAC sensor can be connected to the SenteraWeb cloud platform via an internet gateway. SenteraWeb is the online HVAC platform for remote control, monitoring and data logging. All measured values can be visualized and parameter settings can be adjusted. In case threshold values are exceeded, a notification or warning is sent via email or text message. The day-week schedule enables to optimize the ventilation system in function of the planned activities.
Who is Sentera?
Sentera is one of the leading manufacturers of control solutions for HVAC and ventilation systems. Our mission is to make intelligent HVAC control solutions that are easy to use! We develop, manufacture and promote fan speed controllers, HVAC sensors, HVAC controllers and actuator powered dampers to control airflows and to monitor indoor air quality. Today, the Sentera group counts 8 companies and 150 employees based in 4 different locations. Headquarters and the central warehouse are located in Temse, Belgium. Sentera is a 100 % family owned group of companies. For more information, contact Sentera!
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