In 1901 and 1905, patents for formaldehyde candles were issued by the United States Patent Office. These “so-called candles” (see “Review of Formaldehyde Fumigation,” American Journal of Public Health, page 1048) were used to disinfectant rooms in hospitals and sanatoriums. It was claimed that when lit, they cleaned the air.
U.S. Patent No. 676,814. Formaldehyde Fumigator.
U.S. Patent No. 794,771. Formaldehyde Candle.
Formaldehyde Disinfection in Tuberculosis. Pages 224-229, particularly page 225, Paraform Candle Method. The American Journal of Nursing, December 1911.
Review of Formaldehyde Fumigation. Wm. Dreyfus, American Journal of Public Health, November 1914. In particular, the so-called last paragraph, page 1048.