CO2 meters: how they work, how they relate to preventing the spread of COVID-19
CO2 meters have become one of the fashionable instruments in these times in which Building ventilation is so important in the fight against COVID-19. In this carbon dioxide meter buying guide We explain its functions, what its operation is based on and choose for domestic use, in addition to offering you a careful selection of models.
What are CO2 meters and why is it important to measure carbon dioxide?
CO2 meters are relatively affordable and easy-to-use instruments that measure carbon dioxide. There's also other devices that control “air quality” globally, although the air per se It is heterogeneous. Thus, it can offer the measurement of substances such as CO2 itself, but also particulate matter or other volatile organic compounds, some of which we find in the monitoring carried out by commercial devices such as air purifiers. In domestic appliances it will be common to find air quality devices and not just CO2.
However, CO2 is one of the predominant ones indoors, coming from the respiration of living beings and the volatile organic compounds emanated by construction materials such as paints and other chemicals.
La CO2 measurement is used to determine air quality in buildings, following the current regulations of the Technical Building Code, in the HS Basic Document section 3, related to Indoor Air Quality and concerns “residential buildings, inside them, waste warehouses, storage rooms, parking lots and garages; and, in buildings of any other use, to parking lots and garages. “The vehicle circulation areas are considered to be part of the parking lots and garages.”
In a summary and general way, characterize and quantify the parameters to design ventilation systems that provide the premises with a minimum ventilation flow to guarantee air renewal while expelling the pollutants inherent to the use of each premises. This information will be important later: the minimum air flow must be able to be adapted depending on the occupancy of the room.
For other types of premises, the Regulation of Thermal Installations in Buildings is used or RITE, with five methods including the direct method by CO2 concentration.
| CATEGORY | AIR QUALITY | BUILDINGS | CO2 (PPM) |
|---|---|---|---|
| IDA 1 | Optimum quality air | hospitals, clinics, laboratories and nurseries | 350 |
| IDA 2 | Good quality air | offices, residences (common premises of hotels and similar, nursing and student residences), reading rooms, museums, court rooms, teaching and similar classrooms and swimming pools | 500 |
| IDA 3 | Medium quality air | commercial buildings, cinemas, theaters, assembly halls, hotel rooms and similar, restaurants, cafes, bars, party rooms, gyms, sports venues (except swimming pools) and computer rooms | 800 |
| IDA 4 | Low quality air | Should not be applied | 1200 |
Source | Indoor air categories based on building use + CO2 concentration in indoor air over outdoor air RITE Technical Guide
With an adequate ventilation system, it is possible to minimize the possibility of suffering from sick building syndrome, who defined by WHO Is the set of diseases caused or stimulated by air pollution in these closed spaces.
For this reason alone, air quality control is important, but these months we are also being hit hard by another respiratory disease: COVID-19. The Government has published a guide with recommendations about the use of air conditioning and ventilation systems to prevent the spread of COVID-19.
Among them it stands out that “air renewal is the most important parameter. If possible, a minimum of 12,5 liters per second per occupant is recommended, which is the value that the Regulation of Thermal Installations in Buildings attributes to a good quality air. To ensure this minimum value, you can work in two directions: increase ventilation or reduce space occupation.”
In summary: renewing the air in closed spaces is essential to prevent the spread of COVID-19 and the way to quantify the need for external ventilation air flow is determined by the Regulation of Thermal Installations in Buildings, with the measurement of CO2 concentration as one of the methods used to do so.
Therefore the ideal will be concentrations of 500 ppm of CO2, although it is common to move in the range between 500 and 800 parts per million in volume.
How CO2 meters work
Infrared Absorption. Image licensed under Creative Commons Attribution-Share Alike 3.0 Unported license. Attribution: Oscar2
The most common thing is that the sensor of the Commercial CO2 meters use infrared (Non-Dispersive Infrared), a very common and consolidated gas detection method for those that contain more than one type of atom, such as carbon dioxide, carbon monoxide, methane or sulfur dioxide.
Without going too deep, the operation is based on the different energy absorption of the compounds for this certain wavelength. Thus, carbon dioxide is a gas that absorbs infrared radiation in a characteristic and differential way.
The meter consists of an infrared light sensor and receiver that sends a beam with the CO2 absorption wavelength and receives it back in an attenuated form. The difference between what is issued and what is received is the energy absorbed and this is proportional to the concentration of the gas according Beer-Lambert law.
From this point and taking into account that this guide to CO2 meters is aimed at a non-technical audience, we will look at:
- Si only measures carbon dioxide or also measures other parameters such as humidity, temperature or particulate matter, which also have an impact on our health.
- La precision and resolution in your measurements, the latter being the smallest readable unit or detection limit. In the domestic sphere, it is rare for data relating to precision to be offered, but if so, it is usually a good sign.
- The ease of use. A good screen makes use more comfortable, as long as the interface is clear and supports customizations such as changing languages. However, in this use scenario, those that use icons such as smiling faces or traffic light style color codes to make it more intuitive.
