The alarm threshold of the hydrogen detector is set according to relevant safety standards and actual conditions, as follows:

1. alarm threshold setting criteria

The alarm threshold of the hydrogen detector mainly refers to the following national standard documents:

GBT 50058-2014 Code for Design of Electrical Devices in Explosive Hazardous Environments:

The lower explosive limit (LEL) of hydrogen is 4.00%Vol, that is, when the concentration of hydrogen in the air reaches 4.00 percent, combustion and explosion may occur in case of open flame.

"GBT 50493-2019 Petrochemical Combustible Gas and Toxic Gas Detection and Alarm Design Standard (Official Edition)":

The first-level alarm set value for combustible gas should be less than or equal to 25% LEL.

The secondary alarm setting value for combustible gas should be less than or equal to 50% LEL.

2. specific alarm thresholds

Based on the above criteria, the alarm threshold of hydrogen detector is usually set as:

primary alarm value: less than or equal to 25% of the lower explosive limit (LEL) of hydrogen, I .e. 25% of 4.00 Vol, converted into 1.00 Vol, or converted to ppm value (assuming that the oxygen content in the air is 21%, every 1% Vol is approximately equal to 10000ppm) is 10000ppm.

secondary alarm value: less than or equal to 50% of the lower explosive limit (LEL) of hydrogen, I .e. 50% of 4.00 Vol, converted into a percentage of 2.00 Vol, or converted into ppm value of 20000ppm.