carbon monoxide allowable concentration

例句：

1. 1. Carbon monoxide is a colorless, odorless gas that can be harmful to humans.
   一氧化碳是一种无色无味的气体，对人类有害。
2. 2. The factory was shut down due to high levels of carbon monoxide in the air.
   由于空气中一氧化碳含量过高，工厂被关闭了。
3. 3. The doctor warned us to avoid breathing in carbon monoxide from coal-fired power plants.
   医生警告我们要避免吸入燃煤发电厂产生的一氧化碳。