Alarm value 1. to national standards:

The lower explosive limit (LEL) of hydrogen is 4.00%Vol, that is, when the concentration of hydrogen in the air reaches 4%, there is a danger of combustion and explosion when encountering an open flame. According to the GBT 50493-2019 Petrochemical Combustible Gas and Toxic Gas Detection and Alarm Design Standard (Official Edition) stipulates that the first-level alarm setting value for combustible gas shall be less than or equal to 25% LEL, and the second-level alarm setting value shall be less than or equal to 50% LEL. Therefore, converted into percentage concentration, the primary alarm value of the hydrogen detector is 1% Vol (I. e., the primary alarm is triggered when the concentration of hydrogen in the air reaches 1%), and the secondary alarm value is 2% Vol (I. e., the secondary alarm is triggered when the concentration of hydrogen in the air reaches 2%).

Convert 2. PPM values:

PPM(Parts Per Million) is a unit of parts per million used to express gas concentration. 1% Vol is equal to 10000PPM. Therefore, the primary alarm value (1% Vol) of the hydrogen detector is converted to a PPM value of 10000PPM, and the secondary alarm value (2% Vol) is converted to a PPM value of 20000PPM.

In summary, we can see that the primary alarm value of the hydrogen detector is usually 10000PPM (that is, 1% Vol), and the secondary alarm value is usually 20000PPM (that is, 2% Vol), these values are based on the conversion of national standards and PPM values. However, the alarm value of the hydrogen detector is not a single value, but is determined according to a variety of factors. Therefore, in order to ensure industrial safety and environmental protection, we need to set the alarm value reasonably according to the actual application scenario and safety standards, and regularly calibrate and maintain the hydrogen detector to ensure its accuracy and reliability.