Where do portable gas detectors need to be calibrated?

) Type ) portable gas detector is a newly developed portable detection instrument by our company. It is manufactured in strict compliance with national standards and has passed the inspection of the National Fire Electronic Products Quality Supervision and Inspection Center. < Its main features: < ●High sensitivity, strong reliability< ●Beautiful appearance, easy to hold< ●Long continuous working time< ●With under-voltage indication function< Detection of gases: natural gas, liquefied petroleum gas, coal gas, etc. that are flammable or toxic Gas< Detection range: < Alarm mode: sound and light alarm, the light alarm indication is only a red light display< Response time: &< Alarm volume: &B< Explosion-proof type: intrinsically safe< Explosion-proof mark: C< Power supply: Rechargeable battery section, (Standard charging state) ) Song Dynasty)