fire·damp 
(fīrdămp′)
(fīrdămp′)n.
1. A combustible gas, chiefly methane, often occurring in mines in association with bituminous coal.
2. The explosive mixture of firedamp and air.
- operatic
- operatically
- operatics
- operating expenditure
- operating expense
- operating room
- operating system
- operation
- operational
- operationalism
- operationalist
- operationally
- operations research
- operative
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- operator
- opercular
- operculate
- operculated
- operculum
- operetta
- operon
- operose
- operosely
- operoseness