Gas Detector and Online Gas Analysis System

Gas detector for confined space use


Gas detector for confined space use


Compared with well-known dangerous places such as chemical industry, petrochemical industry and electric power, the security of confined space is often ignored by enterprises.


1. Which industries have confined space:

Poor natural ventilation in confined space can easily lead to the accumulation of toxic and harmful, inflammable and explosive substances or insufficient oxygen content. The industries involved in confined space are very extensive, as follows: chemical industry, coal mine, metallurgy, electric power, construction, municipal engineering, urban gas, sewage treatment, etc.

The confined space is divided into three categories:

A: confined equipment . Such as cabins, storage tanks, vehicle tanks, reactors, pressure vessels, pipelines, flue, boilers, etc.

B: underground confined space. Such as underground pipelines, basements, underground warehouses, underground works, waste wells, mantles, sewage pools, biogas tanks, septic tanks, sewers, etc.

C: confined space on the ground. Such as storage rooms, fermentation tanks, garbage stations, cold storage, granaries, etc.

2. What are the risk factors in confined spaces?

-Toxic and harmful gases

The toxic and harmful gases commonly found in confined spaces are hydrogen sulfide H2S, carbon monoxide CO, ammonia NH3, phosphine PH3, and organic volatile gases VOCs. For example: 
Hydrogen sulfide H2S is produced and accumulated in a confined space such as sewers, septic tanks, and sewage ponds due to the fermentation decomposition of microorganisms. 
The cold storage uses ammonia NH3 as the refrigerant, the granary uses phosphine PH3 as the fumigant, and the pharmaceutical and chemical industry reactors often have various organic gases VOCs such as toluene and acetone.

- Lack of oxygen asphyxiation

Hypoxia in a confined space is mainly caused by two reasons. the first, the respiration of the organism or the oxidation of the substance causes the consumption of oxygen; the second carbon monoxide, nitrogen, methane and other simple asphyxiating gases occupy oxygen in a confined space, resulting in lack of oxygen.

- Flammable and explosive gases

The common flammable and explosive gases in the confined space are methane, hydrogen, etc. Once the explosion limit is reached, the ignition source may explode.

-Other hazards

Any other environmental condition that threatens life or health, such as falling, drowning, collapse, electric shock, mechanical injury, burns, high temperature and other dangerous and harmful factors.

3. Gas safety concentration standard

In order to prevent oxygen deficiency, the oxygen content in the air of the workplace in a confined space should be 19.5% VOL ~ 23% VOL, and when the oxygen content is lower than 19.5% VOL, ventilation should be carried out.

The concentration of combustible gas in the confined space should be less than 10% of the lower limit of the combustible limit or the explosive limit. For example, the concentration of methane should not be higher than 0.5% VOL. For the dismantling of tanker ships and the maintenance of oil tanks and pipelines, the concentration of combustible gas in the air should be lower than the lower limit of the combustible limit or the lower limit of the explosion limit.

For toxic gases, refer mainly to the “Occupational Exposure Limits for Harmful Factors in the Workplace, Part 1: Chemically Harmful Factors” (GBZ2.1-2007) issued by the Ministry of Health of the People's Republic of China. Specifications 4.1 Permissible concentrations of various toxic and hazardous substances are listed in the allowable concentrations of chemical substances in the workplace. For example, hydrogen sulfide does not exceed 10 mg/m3, and carbon monoxide does not exceed 20 mg/m3.


The AGH6100 portable gas detector and AGH1000B gas sampling pump from AIYI Technologies are a part of whole series product for confined space use, if you want to know more about the security of confined space and how to use the gas detector in confined space correctly, please click the link and there are any question we are glad to help.




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