Working humidity range: At a maximum temperature of 40℃, the relative humidity does not exceed 50%. At a maximum temperature of 20℃, the relative humidity should not exceed 90%. 2. Normal operating temperature range: -5℃ to 40℃. Permissible temperature range: -40℃ to 80℃. 3. Altitude: no more than 2000m. When the altitude exceeds this value: 1) The temperature rise of the fuse increases by about 0.5k for every 100 meters above sea level. 2) For every 100 meters of elevation increase, the ambient temperature decreases by about 0.5 ℃ on average. 3) Under normal circumstances, fuses used in open environments can ignore the effect of altitude on rated current and still be selected in accordance with standard conditions. 4) For fuses used in closed environments, if the ambient air temperature of the box or the temperature inside the box does not decrease signiffcantly with the elevation, it can still reach more than 40℃, it is necessary to reduce the rated current capacity. Fuse rated current selection formula