Detecting VOCs to Determine Air Quality

The USB demo kit (Figure 1) for VZ-87 is devised to demonstrate the behavior of SGX Sensortech indoor air quality monitoring solution easily and rapidly. The device enables displaying the VOC and CO2 equivalent values measured by the VZ-87 module based on a metal oxide semiconductor gas sensor, which responds to the presence of VOCs with a decrease in resistance.

The USB demo kit for the VZ-87 module

Figure 1. The USB demo kit for the VZ-87 module

The USB demo kit is capable of performing continuous exposure monitoring and data logging of VOC, humidity, temperature, raw sensor signal, and CO2 equivalent values in environmental conditions for users involved in air quality monitoring or solution developers.

Key Features

The following are the key features of the USB demo kit for VZ-87:

  • Display gas concentration and a chart of actual measurements
  • On-demand display of relative humidity and temperature
  • Real time clock allows for standalone operation
  • Data logging
  • I2C communication (status readings, settings)
  • Pluggable on 5V AC/DC for standalone data logging with RTC
  • Standalone data storage capacity of 1016 data points
  • Storage intervals can be programmed for internal and PC data logging
  • Smaller footprint with dimensions of 73.5 x 17.5 x 16mm (including USB connector)
  • Configuration is simple and quick
  • Data analysis is simple
  • Store time, date, status, , raw sensor value (resistance value in Ohms), estimated CO2 equivalence concentration [ppm], calculated tVOC concentration [ppb], temperature [°C], and relative humidity

Key Applications

The USB demo kit for VZ-87 finds use in the following applications:

  • Assesses the performance of sensors for indoor applications
  • Determines VOCs pollution peaks
  • Monitors CO2 equivalence
  • Helps developing indoor air quality solutions

Advantages of VZ-87

The VZ-87 product has been designed as a demo unit to assess performances in desk area. Algorithm parameters have been described to follow CO2 differences in known conditions with a correlation ratio between VOCs and CO2.

Figure 2 presents VZ-87 monitoring for five days, showing a slight difference between the VZ-87 output and true CO2 concentration determined with another expensive method (NDIR). This is apparently related to the fact that the CO2 gas concentration is not directly measured, but the VOCs, by the MiCS-5524 MOX sensor.

VZ-87 monitoring for five days

Figure 2. VZ-87 monitoring for five days

The sources of these VOCs include human occupancy (exhalation and perfume), pesticides, renovations, microbial action, office equipment, furniture, finishes, fabrics, carpets, cleaning and maintenance supplies.

Exhalation of humans is the only source associated with CO2, explaining the differences between CO2 monitoring in ppm with IAQ devices and NDIR detectors. People spending 95% of their time within a sealed, high-efficiency building will face increased risk of sick building syndrome.

Carbon monoxide, formaldehyde, VOCs, second hand tobacco smoke, and microbial contaminants are the top five indoor air pollutants in accordance with the American Lung Association. In these pollutants, VZ-87 can detect carbon monoxide, formaldehyde, microbial contaminants, and VOCs, and partially detect second hand tobacco smoke.

However, none of the pollutants can be detected with NDIR CO2 module. CO2 detectors are complemented by VOCs detectors through determination of air quality level in correlation with carbon dioxide produced by human presence and VOCs from other sources.

Monitoring Air Quality with SGX VOC Sensors

SGX Sensortech technology helps to detect invisible hazards and pollutants present in air in a superior way. VOC levels measured by SGX sensors can, for example, be converted into an electronic signal. A range of purifiers, cleaners, and ventilation systems can interpret and react upon the electronic signal.

The USB stick developed by SGX consists of its VOC sensing technology and can be directly connected to any PC to measure organic compounds in real time or can perform standalone data logging by plugging it directly into a main socket. This user-friendly configuration helps determining VOC levels in a variety of atmospheres.

Figure 3 presents the VOC concentration log in a typical domestic kitchen monitored for a period of 24 hours, showing the drastic change in the VOC levels caused by the activity within the kitchen. For instance, the VOC levels were considerably increased during food preparation and meal times, and decreased to ambient levels in the night as there was no activity in the kitchen and the domestic heating system was not working.

VOC concentration log in a domestic kitchen

Figure 3. VOC concentration log in a domestic kitchen

About SGX Sensortech (IS) Ltd

SGX Sensortech is a market leader in innovative sensor and detector devices that offer unrivalled performance, robustness and cost- effectiveness.

SGX have been designing and manufacturing gas sensors for use in industrial applications for over 50 years, offering excellent applications support for an extensive range of gas sensors and the expert capability for custom design or own label.

As an independent OEM supplier of gas sensors, we pride ourselves on providing customers with unrivalled product reliability and personal product support via specialist engineers.

SGX gas sensors are built to the highest standards with all pellistor and infrared gas sensors achieving ATEX and IECEx certification, SGX gas sensors are also UL and CSA approved.

Our product portfolio has continued to expand in technology and detectable gases used in a wide range of applications including:-

  • Mining
  • Oil and gas
  • Confined space entry
  • Indoor air quality
  • Industrial area protection
  • Leak detection

This information has been sourced, reviewed and adapted from materials provided by SGX Sensortech (IS) Ltd.

For more information on this source, please visit SGX Sensortech (IS) Ltd.

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