单选题 A gas explosiometer measures the ( ) of combustible gases.

单选题 When doing hot fire analysis, the interval between sampling and hot fire is more than ( ) minutes, or the stop time in the middle of hot work is more than ( ) minutes, you must resamb for analysis.

单选题 ( ) Does not fall under fall protection.

单选题 For ( ) (including) above high work, the "high work permit" should be applied.

单选题 When the chemical equipment is hot repair, the medium that can not be directly used to replace the combustible gas is ( ).

单选题 When the height of the high work is ( ) m, it is called the level 2 high work.

单选题 For hot operation in the no-fire zone, the distance between the oxygen cylinder and the acetylene cylinder is at least ( ) meters.

单选题 High work means work performed above the fall height datum ( ) (inclusive), where there is a possibility of falling.