The Poison Belt by Sir Arthur Conan Doyle

The chamber which was destined to be the scene of our unforgettable experience was a charmingly feminine sitting-room, some fourteen or sixteen feet square. At the end of it, divided by a curtain of red velvet, was a small apartment which formed the Professor's dressing-room. This in turn opened into a large bedroom. The curtain was still hanging, but the boudoir and dressing-room could be taken as one chamber for the purposes of our experiment. One door and the window frame had been plastered round with varnished paper so as to be practically sealed. Above the other door, which opened on to the landing, there hung a fanlight which could be drawn by a cord when some ventilation became absolutely necessary. A large shrub in a tub stood in each corner.

"How to get rid of our excessive carbon dioxide without unduly wasting our oxygen is a delicate and vital question," said Challenger, looking round him after the five iron tubes had been laid side by side against the wall. "With longer time for preparation I could have brought the whole concentrated force of my intelligence to bear more fully upon the problem, but as it is we must do what we can. The shrubs will be of some small service. Two of the oxygen tubes are ready to be turned on at an instant's notice, so that we cannot be taken unawares. At the same time, it would be well not to go far from the room, as the crisis may be a sudden and urgent one."