As explained in the definitions of the NEMA Types 7 and 9. The groups (indicated by letters), which follow the type class, indicate the gas or vapor atmospheres within the hazardous locations.是什么意思_As explained in the definitions of the NEMA Types 7 and 9. The groups (indicated by letters), which follow the type class, indicate the gas or vapor atmospheres within the hazardous locations.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句