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Why measure CO and NO2 in underground parking garages?

Carbon monoxide or CO and nitrogen dioxides or NO2 are toxic gases stemming from motor vehicle sources. When cars with combustion engines move around an enclosed parking garage, they release toxic gases like CO and NO2. Due to their typically low ceiling, underground and enclosed car parks present a particular challenge to ventilation systems. Such a smart ventilation system must prevent the accumulation of toxic gases from motor exhausts in a garage. Toxic gas sensors are optimized to detect and measure these toxic gases in parking garages. 
Carbon monoxide
Carbon monoxide or CO is produced when combustion reactions are not fully completed, either through a lack of oxygen or due to low mixing.  All combustion sources, including motor vehicles, power stations, waste incinerators, domestic gas boilers, and cookers, emit carbon monoxide.

The natural CO content in the ambient air is approximately 0,2 ppm (parts per million). Carbon monoxide affects the human respiratory system. CO attaches itself to red blood cells, preventing the uptake of oxygen. In the short term, this causes headaches and weariness. In the long term, this can cause brain damage even at relatively low concentrations. High concentrations of CO can cause physiological and pathological changes and even death. Since it is a colourless and odourless gas, it is often called the silent killer.

CO concentrations are typically highest in underground garages. CO rises, however, and can seep through to higher levels of buildings. There, it can chronically impact the inhabitants of apartments and office employees. Because the threat of death at high concentrations is real, it is very important to ventilate when CO concentrations rise. With Sentera CO sensor controllers, this can be done automatically. 
Limit values for carbon monoxide
The World Health Organization has established reference values for concentrations and exposure times that are considered harmless for the entire population, including pregnant women and the elderly with (known or unknown) cardiovascular and respiratory problems:
10 mg/m³   (10 ppm)    over the course of 8 hours.
30 mg/m³   (25 ppm)  over the course of 1 hour.
60 mg/m³   (50 ppm)  over the course of 30 min.
100 mg/m³ (90 ppm)  over the course of 15 min.

Additionally, to combat long-term CO exposure, the organization NCBI recommends a limit of 7 mg/m³ (6 ppm) over a 24-hour period. 

Nitrogen dioxide
Nitrogen dioxide or NO2 is generally considered a useful indicator for measuring and judging air pollution stemming from motor vehicle sources. NO2 is part of the NOx gas group. It is a by-product of fuel burning and comes primarily out of car exhaust pipes. 
Breathing air with a high NO2 concentration can irritate airways in the human respiratory system. Studies show that symptoms of respiratory diseases, especially asthma, can aggravate at short-term exposures. Long-term exposure to NO2 may contribute to the development of asthma and other respiratory diseases.
Sentera offers a complete range of toxic gas sensors that measure NO2 concentrations. They are available in different enclosures and with different supply voltages.

Limit values for nitrogen dioxide
The WHO recommends an annual mean NO2 limit of 10 μg/m³ (5 ppb). It has a separate 24-hour mean of 25 μg/m³ (13 ppb). However, these are mean values over long periods. For short periods, different limit values for NO2 exist. Some studies have shown that for short-term exposure, an acute value of 5 ppm is considered safe. Other studies considered an 8-hour time window and concluded that a concentration of no more than 1 ppm is acceptable. It is advisable to keep the limit value for NO2 as low as possible. 

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