Gas and Air quality
Gases / CO2
There are often complains about indoor air quality, but translating the complaints to actionable data to identify and fix the problems is not easy. This is just one good reason to analyze the air quality over time.
Gas sensors exists for many different gases and purposes. Some gases are dangerous even in small concentrations and some are flammable. The different properties of different gases require specific sensors for each type of gas.
Some applications for gas sensing are:
- Indoor CO2 sensing – monitor levels and adjust ventilation or control HVAC directly
- Safety applications – generate warnings and alarms if gas concentrations gets over recommended levels.
- VOC – monitor, alarms and record levels of solvent vapors in the air
Some common gas sensors are:
The air contains about 0.04% CO2. When the concentration reaches about 0.1%, some people can begin to feel drowsy, and that level can easily be reached in a crowded room. Controlling CO2 is important for productivity and health.
CO2 meters are usually optical. They emit infrared light through a tube and a sensor picks up certain wavelengths that are absorbed by the gas. Although common CO2 sensors are quite sensitive, they do not have enough resolution to monitor outside CO2 variations. For outside air monitoring, lab grade sensors are recommended.
The output from most CO2 sensors is analog, and matches the ezeio inputs well. Even better accuracy can be had using a Modbus communicating CO2 sensor.
CO is a very dangerous gas even in small concentrations. It has no smell or color. Luckily the sensors required to detect it are simple, low cost and readily available. Some states have laws requiring CO detectors in homes and businesses.
While monitoring CO with the ezeio is technically possible, the ezeio is not designed as a life safety device, and should not be relied on for CO detection.
There are simple low cost sensors for most VOC’s and Hydrocarbons that can be used with the ezeio system. The output is typically analog (0-5V or 4-20mA) so they can connect directly to the analog inputs of the controller and be monitored and recorded.
While we sometimes get the question, Oxygen monitoring only has limited applications. It can be interesting in some lab environments where cryogenics are used to monitor for Oxygen levels, as liquid Helium, Nitrogen and Argon can displace Oxygen and cause danger. This is a life safety application, so alarming systems designed for that specific purpose should be used.