Application of CO sensor in CO alarm of underground garage

Carbon monoxide (CO) is a colorless, odorless, toxic gas. With the popularity of private vehicles and underground garages, poisoning incidents caused by it have frequently appeared in the news. In recent years, the state has also begun to require carbon monoxide detection systems in underground garages. For example, Article 8.6.3 of the "Jiangsu Province Green Building Design Standard" stipulates: "Underground garages with mechanical ventilation should monitor and control CO concentration in real time."

Underground garages are closed or semi-closed buildings, so air circulation is naturally not smooth. Environmental pollution in underground garages mainly comes from automobile exhaust, the main component of which is carbon monoxide. The most significant impact on human tissue hypoxia, heart and brain is
when carbon monoxide in the air reaches a certain concentration, and the CO alarm will sound immediately. Carbon monoxide gas is a colorless, odorless, non-irritating, toxic gas. When inhaled, it causes hypoxia in the human body and even threatens life.

1. The hazards and generation of carbon monoxide (CO) in garages

Carbon monoxide is colorless, odorless, and tasteless, and is very harmful to the human body if inhaled. It will combine with hemoglobin to form carboxyhemoglobin, which causes hypoxia. The most common symptoms of carbon monoxide poisoning are headache, nausea, vomiting, dizziness, fatigue, and weakness. Exposure to carbon monoxide may seriously damage the heart and central nervous system, and there will be sequelae.

According to tests, when the carbon monoxide concentration in the air reaches 50ppm, a healthy adult can withstand it for 8 hours; when it reaches 200ppm, a healthy adult will experience mild headache and fatigue after 2 to 3 hours; when it reaches 400ppm, a healthy adult will experience forehead pain within 1 to 2 hours, and become life-threatening after 3 hours; when it reaches 800ppm, a healthy adult will experience dizziness, nausea, and convulsions within 45 minutes, lose consciousness within 2 hours, and die within 2 to 3 hours.

The production of carbon monoxide in underground garages mainly comes from car engines. When the engine is idling, due to incomplete combustion of gasoline, exhaust gas containing a large amount of CO will be produced. Underground parking lots are closed environments, and vehicles frequently enter and exit. The exhaust gas emitted is not easy to be discharged, and a large amount of CO gas is easily accumulated, causing the parking lot to be filled with pungent odors, which is harmful to people's health. Therefore, underground garages and parking lots should be equipped with air supply and exhaust systems to replace with fresh air. The CO content in underground garages should be lower than 25ppm for a long time and should not be higher than 37.5ppm for a short time.

2. Domestic and international CO standards and garage ventilation requirements

1. "Industrial Enterprise Design Hygiene Standard" GBZ1-2002

Regulations: The maximum allowable CO concentration in the workshop is 30 mg/m3. When the operating time does not exceed 30 minutes at a time, the allowable CO concentration can be relaxed to 100 mg/m3. When the operating time is within 10 to 20 minutes, the maximum allowable concentration is 200 mg/m3.

2. Occupational Exposure Limits for Hazardous Factors in the Workplace GBZ2-2002

Permissible concentration of toxic substances in workplace air

Time-weighted allowable concentration: It is required to collect representative samples, and divide the sum of the products of each exposure duration and its corresponding concentration within an 8-hour working day by 8 to obtain the 8-hour time-weighted average concentration.

Permissible concentration for short-term exposure: Generally, air samples are collected for contact time of 15 minutes; when the contact time is shorter than 15 minutes, the time-weighted average concentration of 15 minutes is used for calculation.

3. Ambient Air Quality Standard GB 3095-1996

This standard specifies the concentration limits that each pollutant is not allowed to exceed:

Category I areas include nature reserves, scenic spots and other areas that require special protection.

Category II areas include residential areas, mixed commercial, transportation and residential areas, cultural areas, general industrial areas and rural areas determined in urban planning.

Category III areas are specific industrial areas. Category I areas implement the first-level standard, Category II areas implement the second-level standard, and Category III areas implement the third-level standard.

4. "Indoor Air Quality Standard" GB/T18883-2002

Indoor air quality standards:

5. European II emission standards

Taking a car with a design passenger capacity of no more than 6 people (including the driver) and a maximum total mass of no more than 2.5t as an example, my country will implement the European II emission standard after January 1, 2004: gasoline cars shall not exceed 2.2g/km of carbon monoxide and 0.5g/km of hydrocarbons; diesel cars shall not exceed 1.0g/km of carbon monoxide, 0.7g/km of hydrocarbons, and 0.08g/km of particulate matter.

6. "Energy-saving Design Standard for Public Buildings" GB50189-2005

The ventilation system of the underground parking garage should set the fan to start and stop (number of units) according to the usage or automatically control the operation according to the CO concentration in the garage. The permissible concentration of CO in the parking garage is specified as (3~5)×10-6 m3/m3.

7. Foreign regulations on CO concentration limits in garages

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-hour CO exposure level - less than 25ppm. (World Health Organization General Principles)

ANSI/ASHRAE 62-1989: Even spaces that are not continuously occupied (such as parking garages) require ventilation, with CO exposure limits of 35 ppm for 1 hour and 9 ppm for 8 hours. (USA)

Canada: Maximum acceptable CO levels in parking garages—30 ppm for 1 hour, 13 ppm for 8 hours.

Finland: Parking garage hygiene regulations limit CO exposure levels to 30 ppm for an 8-hour average and 75 ppm for a 15-minute average

France: Parking garage CO concentration is 100 ppm for 20 minutes and 50 ppm for 8 hours.

Germany: For closed parking facilities, the average value of CO concentration during a half-hour period does not exceed 100 pp (measured at 1.5 m above the ground).

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

8. Garage ventilation requirements in different countries

Japan and South Korea: Ventilation volume 6.9~8.3 L/(s·m2), depending on garage size and vehicle type.

Finland: The parking lot ventilation volume of the office building is 2.7 L/(s·m2).

Sweden: Building laws require ventilation for large detached garages - at least 0.9 L/(s·m2).

France: For closed garages with a floor area greater than 20,000 m2, ventilation volume – 167 L/(s·car).

United States: Enclosed parking garages require 7.5L/(s·m2).

Germany: Enclosed parking facility ventilation volume: small garage 1.67 L/(s·m2), large garage 3.35 L/(s·m2)

China: The requirement is 6 ventilation changes per hour, which is very close to the French regulations.

9. Conclusion: Based on the above data and the plume theory, the CO starting concentration of the intelligent induced fan should be set to 30~40ppm.

3. Purpose of the Carbon Monoxide (CO) Detection System in Underground Garages

At present, there are two main purposes for installing a carbon monoxide detection system in an underground garage:

1. Regular ventilation ensures that the carbon monoxide concentration in the garage is below the hazardous level for safety reasons.

2. Exhaust air according to the carbon monoxide concentration in the underground garage to avoid energy waste caused by excessive exhaust frequency, which is an energy-saving consideration.

4. Function and setting of carbon monoxide (CO) detection system in underground garage

As shown in the figure above, the underground garage carbon monoxide monitoring and control system mainly consists of three parts:

1. Carbon monoxide CO sensor

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

1. Electrochemical Carbon Monoxide Sensor (CO Sensor) TGS5042 Description:

TGS5042 is a battery-driven electrochemical carbon monoxide sensor developed by Figaro. Compared with existing electrochemical sensors, it has the following advantages: the electrolyte is environmentally friendly; there is no risk of electrolyte leakage; the carbon monoxide concentration can be detected up to 1%, the operating temperature range is wide (-5℃ ~ 55℃); the sensitivity to interfering gases is very low. This sensor has the characteristics of long service life, good long-term stability and high accuracy, and is one of the few ideal sensors available for digital display. OEM customers will find that the barcode of each sensor can be used to print the data of each sensor separately, allowing users to avoid expensive gas calibration procedures and allowing individual sensors to be tracked. The CO sensor TGS5042 adopts the appearance design of the standard AA battery size.

2. Features of electrochemical carbon monoxide sensor (CO sensor) TGS5042:

* Battery powered

* High selectivity/reproducibility for carbon monoxide

* Highly linear output characteristics for carbon monoxide

* Easy calibration

* long lasting

* UL certified

* Meet the requirements of UL2034, EN50291 and RoHS

3. Electrochemical carbon monoxide sensor (CO sensor) TGS5042 typical application:

* Residential and commercial carbon monoxide detectors

* Industrial carbon monoxide monitoring

* Indoor parking lot ventilation control

* Fire alarm