Four-in-one gas detector, also known as composite gas detector, can be used for routine detection of four kinds of gases, respectively: combustible gas EX, carbon monoxide CO, hydrogen sulfide H2S, oxygen O2, four-in-one gas detector in the detection of these gases, there are relevant data standards.

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Methane (CH₄)
1. Exceeding 1.00%LEL: The gas detector will alarm.
2. Below 1.00%LEL: Considered normal.
3. Exceeding 5%LEL: Risk of explosion in the presence of an open flame. Hot work (e.g., welding) is prohibited.
4. Exceeding 25%LEL: May cause headaches, dizziness, fatigue, difficulty concentrating, and increased heart and respiratory rates. Step outside for fresh air every 30 minutes.

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Carbon Monoxide (CO)
1. Exceeding 24 ppm: The gas detector will alarm.
2. Exceeding 50 ppm: Maximum allowable concentration for adults.
3. Exceeding 200 ppm: Mild headache, dizziness, and nausea may occur after 2–3 hours. Step outside for fresh air every 30 minutes.
4. Exceeding 400 ppm: Evacuate the area immediately and report to the responsible personnel.

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