1. More rain all year round, humidity, salt fog heavier areas.
2. The working environment is humid, there is water vapor place.
3. Elevation of not more than 2000m.
4. The working environment contains sand dust, dust and other non-flammable dust.
5. The work environment contains weak acid, weak base and other corrosive gases.
6. As oil, chemicals, food, pharmaceutical, military, warehousing and other places lighting.