The HR-1 humidistat has a sensor made of human hair, the company says. When the relative humidity of the surrounding air increases, the length of the hair increases, and vice versa. The change in length is transferred to a microswitch or a slide-wire potentiometer, says the manufacturer. This model has a tamperproof setpoint, supplied with two kinds of covers, one transparent and one white for concealed setting function. It has a range of 10% to 95% RH.
Regin HVAC Products, 273 Canal Street, Ste. 222, Shelton, CT 06484; 800-394-2739; www.regin.com (website).