OSHA sets a minimum limit of 19.5% oxygen for work areas. Working in concentrations below this level requires use of a supplied air source.是什么意思_OSHA sets a minimum limit of 19.5% oxygen for work areas. Working in concentrations below this level requires use of a supplied air source.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句