Indoor Air Quality Monitoring

COVID-19 can be spread through the air when people infected by the virus exhale or speak, but unlike CO₂, COVID-19 spreads through droplets, called aerosols, which are too small to be seen and can accumulate in poorly ventilated spaces. Due to cost and efficiency, it is difficult to measure the volume of aerosol transmission. However, as both CO₂ and COVID have similar ventilation requirements, it is possible to extrapolate the airflow of space by identifying the volume of CO₂ within an indoor space.

If a detector finds a high concentration of CO₂ gas, it means that there is insufficient ventilation and it is therefore more likely for respiratory illnesses to spread to occupants within the same room. For spaces that hold large volumes of occupants such as schools, universities, and offices, it is important to consider adequate ventilation as a priority in contributing to the decrease in transmission.

Normal air is a composition of Nitrogen (78%),Oxygen (20.9%),Argon (0.9%),Carbon Dioxide (0.04%) & tiny amounts of other gasses.

CO₂ levels in normal ambient (outdoor) air is 400ppm. An average of 1500 ppm CO₂ concentration over the occupied period in a space is an indicator of poor ventilation and occupants will begin to experience symptoms of drowsiness due to poor air quality. Where CO₂ readings are consistently higher than 1500ppm, ventilation, whether mechanical, natural or a combination should be taken to reduce CO₂ build-up.

Ideally, providing sufficient ventilation to ensure CO₂ readings are consistently kept below 1000ppm is highly recommended.

Effects from poor ventilation can be experienced immediately or years later. Poor ventilation also enhances the risk of transmittable diseases and airborne viruses.

Some common symptoms associated with poor air quality include:

• Irritation of the eyes, nose, and throat
• Headache
• Dizziness and fatigue
• Nausea

In extreme cases of poor ventilation, the build of CO₂ can lead to issues with respiration, headaches and decreases in mental capacity. The levels at which these negative impacts generally take hold is at CO₂ levels of around 3000-5000 ppm.

Respiratory illnesses and COVID-19 are not the only dangers that make indoor air quality monitoring even more vital in everyday life. From an increase in traffic pollution to bushfire smoke which can present a danger to sufferers of pre-existing respiratory conditions such as asthma, the maintenance of good air quality is vital for health, comfort and performance.

An easy way to measure CO₂ levels is by utilising a CO₂ sensor. These sensors are available in a range of fixed and desktop models providing users with the reassurance of the quality of the air in the monitored space. The sensors monitor the CO₂ gas levels actively over time and can provide live feedback to ensure that users can make informed decisions to improve indoor air quality within the room.

Fixed CO₂ Sensors such as the Elsys CO₂ Sensor can assist in creating a wireless network of sensors to ensure accurate CO₂ readings in different rooms. Sensors are wall-mounted in each room of concern and transmit real-time data using the LoRaWAN networking protocol to a cloud-based platform where the data will be accessible on an easy-to-use interface such as on the LiveSense Platform.

One of the fastest and easiest ways to improve indoor air quality is to open windows and increase the area that the air can enter and exit the indoor space. This may not always be feasible in high rise office buildings or may not be the best solution with external factors such as extreme weather conditions such as low outside air quality from causes such as bushfire smoke and more.

Additional means of improving ventilation are mechanically based. These include ventilation systems as well as air purifiers. Ventilation systems assist in bringing in fresh air and removing CO₂ from a room whilst air purifiers work to filter the air quality within the room. Air purifiers are designed to work by mechanical filtration, drawing in air and pushing it through a fine-mesh filter. This helps filter out airborne viruses, bacteria, and particulate matter. Air purifiers can’t fully eliminate the transmission of viruses but can help reduce risk. However, caution is advised for air purifiers that utilise UV functionality as studies have shown that they may be harmful to users. For more information about what to look for in an air purifier can be found in a great article by the University of Melbourne’s Cleaner Air research team.

Calibration is a comparison between a known measurement (that is the standard) and the measurement using your instrument. An instrument is calibrated to ensure reliability and to determine the accuracy of the measurements. How often an instrument should be calibrated would depend on it instrument itself and what it is used for. However, a shorter time span between calibrations means fewer questionable results.

All CO₂ monitors require calibration to ensure accurate and reliable measurements are being collected. Some CO₂ sensors can be calibrated by using a known concentration of CO₂ gas. If you are using a CO₂ monitor with a self-calibrating function such as the ERS CO₂ sensor, then you don’t have to worry about regular calibrations because the instrument will do it for you.

The ERS CO₂ Sensor is maintenance-free in normal environments thanks to the built-in self-correcting ABC (Automatic Baseline Calibration) algorithm. The theory behind ABC calibration is that for indoor air quality use, at some point each day a room is unoccupied, and the CO₂ level should return to 400 ppm, the same as outdoor air. By storing the lowest CO₂ readings taken for approximately 8 days and then comparing the lowest stable value with the meters 400 points, it adjusts the zero point according to the new value.

This sensor has a life expectancy of at least 15 years and does not require any further calibration when used in normal indoor air applications. This means, for the end user you have a reliable and cost-effective monitoring solution for IAQ.
The ABC Algorithm will not work however if a space is constantly occupied. For these applications, the ABC function must be turned off and the sensor must be manually calibrated every two or three years. Manual calibration requires trained service technicians. can assist with that. With service centres located nationwide, Air-Met Scientific's experienced team of service technicians can assist with manual and traceable calibrations for CO₂ monitors at your site.