What does 2 15 in the blue sky alarm system stand for?

"2 15" refers to the situation that the concentration of harmful gas monitored exceeds the safety limit stipulated by national standards, and measures need to be taken in time to avoid endangering human health. Blue Sky Gas official website shows that the "2" in this number represents the first-class warning line, indicating that the concentration of harmful gas monitored has exceeded the first-class safety limit set by the state. "1" stands for the second-level warning line, indicating that the monitored concentration of harmful gas has exceeded the second-level safety limit set by the state. "5" stands for specific harmful gas types, which can be different according to different monitoring equipment and monitoring items.