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To the Editor.—
A 5-cm square of thin, porous polyethylene sheet can be cut to size, a thin strip of adhesive attached to the inner edge, and applied to the upper lip just below the nostrils. This hypoallergic material can be obtained in any department store at the notion counter. It is approximately 3 mm thick, and will filter out particles 1/60,000 cm or larger. A new one can be used as often as desired, as the cost is about 1 cent per filter. It can be used at all times and in all places that the patient feels it helps, and is comfortable even during sleep. The valvular action allows free expiration, and a snug fit moves into place on inspiration. It can also be used over the stoma of laryngectomies and after tracheotomy. The material is commonly called "art foam." The photographs show its application.
Hargett ER. A Practical Nasal Filter. JAMA. 1972;219(9):1213. doi:10.1001/jama.1972.03190350049026