1.   A cloud of poisonous gas escaped from the chemical plant.

2.   By then the influence of anaerobic Decomposition and poisonous gases will have become obvious.

3.   Carbon monoxide is a highly poisonous gas, mostly produced by cars.

4.   Carbon monoxide is a highly poisonous gas.

5.   Carbon monoxide is present in all cigarette smoke and is also the poisonous gas in car exhausts.

6.   Consequently poisonous gases arise to adversely affect the medium.

7.   If hydrogen sulfide or some other poisonous gas is detected, Donahue dons an airtight breathing device and a hard hat.

8.   In addition, there was the constant danger of poisonous gas.

9.   Some emit poisonous gases which kill or temporarily paralyse any insects who attempt a meal.

10.   The barrier of poisonous gas appeared to be less penetrable than the rock that had been tunnelled through.