Air Quality Monitoring in Public Places

People pay more attention to the quality of urban air and household air every day, but not enough attention is paid to the air quality of public places.

1. Excessive indoor air pollutants in public places

In some public places, such as large shopping malls and supermarkets, during the peak hours of passenger flow, the carbon dioxide exceeds the standard. In addition: newly renovated hotels, entertainment venues, etc., Due to poor ventilation conditions and poor quality of building decoration materials, the indoor environment is seriously polluted.

2. The central air-conditioning system in public places is seriously polluted

There are many centralized air-conditioning and ventilation systems in public places that are not cleaned for a long time, resulting in the formation of a large number of pollutants in the air-conditioning pipes. After a long period of operation, the indoor air quality will drop sharply, which may easily lead to the spread of respiratory infectious diseases.

3. Insufficient input of fresh air volume of central air conditioning system

According to regulations, the minimum fresh air volume in public places should reach 30 cubic meters per person per hour to solve the air quality problems caused by confined spaces. However, since the energy consumption of processing fresh air accounts for more than 20% of the energy consumption of air conditioners, some operators turn off the fresh air volume to a very small amount or even close it completely in order to save operating costs, resulting in poor air circulation and inability to replace fresh air. Indoors, harmful gases cannot be discharged, causing indoor air pollution.

The underground parking garage is poorly ventilated like a gas chamber, CO monitoring is necessary

sensors for Air Quality Monitoring in Public Places

The underground parking garage is a closed environment. Vehicles come in and out frequently, and the exhaust gas is not easy to discharge, resulting in a choking smell in the parking, which often contains a large amount of carbon monoxide that is harmful to the human body.

When the car is idling and the external circulation of the air conditioner is turned on, the carbon monoxide will accelerate into the car with the exchange of air. Even if you only turn on the internal circulation of the car, the carbon monoxide deposited in the underground parking garage will slowly penetrate into the car through the gap of the car,damaging people's health..

Air Quality Monitoring in Public Places

CO concentration limits in garages in different countries

  • WHO (World Health Organization) 1987: Recommended CO exposure level: 1 hour CO exposure level - no more than 75ppm for light workers, 50ppm for heavy workers; 8 hours CO exposure level - less than 25ppm. (General rules of the World Health Organization)
  • China: The ventilation system of the underground parking garage according to the "Design Standard for Energy Conservation of Public Buildings" (GB50189-2005) should be controlled by timing start and stop (number of units) of the ventilator according to the usage or automatic operation control according to the CO concentration in the garage. The allowable concentration of CO in the parking garage is specified as (3~5)×10-6 m3/m3.
  • USA: ANSI/ASHRAE 62-1989: Ventilation required even for spaces that are not continuously occupied (eg parking garages), CO exposure limits - 35ppm for 1 hour, 9ppm for 8 hours.
  • Canada: Maximum acceptable CO levels for parking garages - 30ppm for 1 hour, 13ppm for 8 hours.
  • Finland: Parking garage health regulations limit CO exposure levels - 30ppm average for 8 hours, 75ppm average for 15 minutes
  • France: CO concentration in parking garage is 100ppm for 20 minutes and 50ppm for 8 hours.
  • Germany: Closed parking facility, average CO concentration - not more than 100pp over half an hour (measured at 1.5m above ground).

While regulatory requirements vary from country to country, limiting long-term CO exposure levels to 25 ppm satisfies all of the above laws.

Underground Garage Carbon Monoxide Monitoring System

The carbon monoxide monitoring and control system of the underground garage mainly consists of three parts:

1. Carbon monoxide CO sensor

ME4-CO CO sensor

▲ ME4-CO CO sensor

The on-site carbon monoxide concentration detector can detect the carbon monoxide concentration value in the garage in real time at multiple points, and can upload the data to the controller for centralized display.

2. Acquisition controller

The data acquisition controller is used to centrally display the carbon monoxide concentration value of each monitoring point. At the same time, the controller is associated with the exhaust system. When the carbon monoxide concentration exceeds the preset alarm value, it can automatically alarm or control the start of the exhaust system.

3. Linkage fan

The fan is linked by the controller. When the carbon monoxide concentration exceeds the standard, the fan is automatically started; when the carbon monoxide concentration returns to normal, the fan automatically stops.

According to the toxicity of carbon monoxide, it can be seen that 50ppm is the maximum limit that healthy adults can bear within eight hours, and it is generally recommended that the alarm value be set at 30ppm. When the concentration value exceeds 30ppm, it will automatically remind and exhaust.

Sensor Application in Subway Environment Control System

gas sensor for Air Quality Monitoring in Public Places

When taking the subway, everyone may have the following experience: when taking the subway during the rush hour, you often feel dizzy and feel breathless; when there are few people, you will feel the air conditioner is too cold.

This is because the traditional subway environmental control system is not intelligent continuous cooling and exhausting. Cooling and exhaust air volumes are almost constant all the time.When there are many people, the carbon dioxide content is too high and the oxygen content is insufficient. It will cause discomfort to the human body, but when there are few people, it feels too cold.

The subway is usually underground, and the flow of people is very large. The monitoring of environmental parameters is very important, which is related to people's life safety and physical health. The use of temperature and humidity sensors, CO2 sensors, PM2.5 dust sensors and other environmental sensors can ensure that the air quality in the subway station, creating a comfortable environment for everyone.

The subway environmental control system is an important means to maintain the stability and safety of the air in the subway station and on the subway. The air-conditioning and ventilation system is operated for a long time, and the power consumption is very large, accounting for about 40% of the entire subway power consumption. As an indispensable part of the control system, the application of environmental sensors in the subway is becoming more and more important.

Air quality

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The first six FAQs. Use the search bar above to reveal more!

Is the Dust Sensor Wired when Shipped?

Laser dust is wired, infrared dust is not wired.

How to Install and Place the Infrared Dust Sensor?

It must be installed vertically. Keep away from artificial air flow such as fans. When used in air purifiers, the front and rear of the fan cannot be installed. Optionally install it on one side of the shell, but keep vents on the shell to ensure that the external air can diffuse in.

Can the Two Voltages of Mq-7 Exist All the Time, or Do They Need to Be Powered Alternately? if It is an Alternate Power Supply, What is the Appropriate Power Supply Time?

It requires alternate power supply. Please check the information on the product manual. This sensor is powered by 1.5V and 5V alternately. The low temperature and low voltage (1.5V) state can detect CO, and the high voltage (5V) is the desorption process. The recommended 5V voltage duration is 60s, 1.5V voltage duration is 90s to alternately supply power. Since it is a desorption process at 5V, it is normal for the voltage to drop when CO is 150ppm.
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