Frequently Asked Questions about Four-in-One Gas Detectors
① What kinds of gases can a four-in-one gas detector measure? It supports optional configuration and continuous monitoring of 1 to 4 types of gases: combustible gas, oxygen, carbon monoxide and hydrogen sulfide.
② Why are four gases including combustible gas, oxygen, carbon monoxide and hydrogen sulfide equipped for the four-in-one gas detector? These four gases exist widely in various working environments. Before workers enter confined spaces such as reaction tanks, storage tanks, containers, sewers, other underground pipelines, railway tank cars, cargo holds of ships, tunnels and other workplaces, on-site gas detection must be completed outside the confined space. At this time, a multi-gas detector with an internal pump must be adopted. The distribution and types of gases vary greatly at different heights (upper, middle and lower parts) inside confined spaces. Combustible gases are usually lighter than air and mostly accumulate in the upper zone; carbon monoxide has a similar density to air and generally distributes in the middle zone; heavier gases such as hydrogen sulfide gather at the lower zone. Meanwhile, oxygen concentration is also an essential detection item.
③ What do the measurement units on the display panel of the four-in-one gas detector mean? The unit depends on the gas being measured, and different gases adopt different units. High precision is required for toxic gas detection, which usually uses ppm, referring to the number of target gas molecules per one million gas molecules. For scenarios demanding higher precision, ppb is adopted, meaning the number of target gas molecules per one billion gas molecules. Oxygen is generally measured in volume percentage (vol%). Combustible gas adopts the concept of Lower Explosive Limit (LEL). For example, 30%LEL means the current gas concentration reaches 30% of the explosion limit concentration.
④ Where can four-in-one gas detectors be applied? They are suitable for sites with explosion risks and toxic gas leakage, underground pipelines, mines and other locations, covering agriculture, chemical industry, construction, electric power, fire protection, natural gas, general manufacturing, hazardous materials management, iron and steel industry, petroleum and petrochemical industry, sewage treatment, and all other sites where toxic gas may be generated.
⑤ What does "Ex" marked on the four-in-one gas detector label stand for? If "Ex" appears on the housing or packaging label, it stands for explosion-proof. If displayed on the screen, it indicates combustible flammable gas, with %LEL (percentage of Lower Explosive Limit) as the corresponding measurement unit. A standard four-in-one gas detector monitors H₂S (hydrogen sulfide), CO (carbon monoxide), O₂ (oxygen) and Ex (combustible gas).
