Parameter

Limit Level

Action

Methane (CH₄)

>0.5% v/v (or >10% LEL)

1) Prohibit smoking, all fires, and naked flames.

2) Post warning signs.

3) Increase ventilation to lower the methane to less than 0.5% v/v.

>1% v/v (or >20% LEL)

1) Stop all the construction activities in the affected area.

2) Evacuate personnel who are working in the affected area.

3) Prohibit entry to the affected area.

4) Increase ventilation to lower the methane level to less than 0.5% v/v

Carbon Dioxide (CO₂)

>0.5% v/v

1) Increase ventilation to lower the CO₂ level to less than 0.5% v/v

>1.5%

1) Extinguish all fires and naked flames.

2) Stop all the construction works in the affected are.

3) Evacuate personnel in the affected area

4) Prohibit entry to the affected area

5) Increase ventilation to lower the CO₂ level to less than 0.5% v/v

Oxygen (O₂)

≤18% v/v

1) Stop all the construction activities in the affected area.

2) Evacuate personnel in the affected area.

3) Prohibit entry to affected area.

4) Increase ventilation to increase the oxygen level to above 18% v/v