The fumes of burning sulphur are also a very efficient means of control where the conditions are such that this method can be used, readily destroying the insect in all stages, including the egg. The treatment is inexpensive compared with the use of hydrocyanic-acid gas and offers much less risk of danger to human beings. There is, however, a considerable risk of injury to household fabrics, furnishings, and wall papers from the strong bleaching quality of sulphur fumes. This danger will be somewhat diminished if the fumigation can be done at a time when the room or house is thoroughly dried out, as in winter by a furnace or other heating system. Further precautions should be taken by removing all metallic surfaces from the room or building, or by protecting them with a coating of vaseline. Two pounds of sulphur are recommended for each 2,000 cubic feet of space, and the building should be closed for the treatment for at least 5 or 6 hours, or preferably for 24 hours. Sulphur candles may be used where available, or the sulphurous gas or fumes can be generated by burning the sulphur in a dish placed in the center of the room, and for protection set within a larger vessel. Thorough-going precautions must be taken to prevent accidental overflowing or the starting of a fire, and after the fumigation the house should be given a thorough airing. Other gases have been experimented with, such as formalin and the vapors of benzine, naphthaline, and camphor, but these gases are of little value. Similarly, insect powders are of little value, largely from the difficulty of getting them into the crevices and other places of concealment of the insects. Where the use of poisonous gas is difficult or objectionable, especially if only one room is infested, the pests may be eliminated by the application of kerosene, benzene, or any of the lighter petroleum oils, by means of a small hand sprayer. The liquid should be directed at close range into all cracks and crevices in the walls and behind loose wall paper. Open spaces back of baseboards and picture moldings should be liberally treated. The bedstead and springs should receive the same attention, care being taken to spray the liquid into all crevices. The mattress should likewise be carefully gone over. All seams and spaces beneath tuftings should be thoroughly dosed. At the expiration of 10 days the entire treatment should be repeated with the same care, regardless of whether any bugs are seen or not. If the two applications are made with painstaking care this should be sufficient for complete eradication.