I was in our attic with one unidentified male companion. There was a large box full of coal which was supposedly a furnace of some sort. I raked over the coals with a long pool bridge to see if I could start a fire. (Had played pool recently). The fire started and began to flame very high (was not conscious of heat). Flames were somewhat confined by cardboard which didn't seem to burn. When flames reached ceiling we looked for fire extinguisher. Male companion get extinguisher which was hanging up in rafters; got it by climbing up in rafters; handed it down to me (hose type extinguisher). Extinguisher was leaking fluid and we weren't sure we could use it to put out fire. Was not panicky due to fire; didn't seem important after we got the extinguisher.