The basic components of<unk> s are foam, paper, or a substance which acts as a condensation and absorption surface. The material is often impregnated with hygroscopic salts such as calcium chloride, to enhance the water-retaining capacity.<unk> s used for laryngectomees are mostly hygroscopic.<unk> s can vary in size but they are designed to fit all adhesives or other attachment devices within a certain product line.<unk>  cassettes for tracheotomy patients vary in size and are usually a bit larger than for laryngectomy patients. Air openings are at the side or at the front of the<unk> . Some designs use crossbars to prevent clothing from blocking. Usually a rim on the lid helps to find the correct finger position for occlusion. Hands-free A hands-free<unk>  enables laryngectomees to speak without requiring finger occlusion. The device consists of a combination of<unk>  and an automatic speaking valve. The valve closes automatically when exhaling air for speaking, enabling the pulmonary air to be diverted through the voice prosthesis into the esophagus. It reopens automatically when exhalation decreases. Besides that, the hands-free<unk>  enables easy removal in case of coughing, or even an adjustable cough relief valve, to release the air that is built up during coughing. In some devices, speech membranes in different strengths can accommodate different speaking pressures.
Heat and moisture exchanger
Air purifier
Air ioniser
Nebulizer
Vacuum insulated evaporator
Respirometer
Membrane oxygenator
Hand sanitizer