breathed air&unbreathed air點解?

breathed air is air suitable for us to live in & unbreathed air is polluted , toxic fumes such CO , H2S.... etc exceeding the safety limit that make us sick , unhealthy , or carcinogenic to live in .

2009-09-18 10:32:04 補充：
因為你用英文問 . 簡單可呼吸空氣 , 不含超過法律規定有害氣体 , 縣浮粒子 , 可安全吸用 . 不可呼吸空氣則反之 .

Breathed air are the air that we breathed, there will be a larger amount of cabon dioxide.And the amount of oxygen will decrease.

undreathed air are the air that we haven't breath, the air around us. It contain a smaller amount of carbon dioxide than breathed air, the amount of oxygen stay normal.