TSI is no stranger to a good test. Founded in 1961 as Thermo-Systems Inc., TSI makes sensors and instruments used in a wide range of environmental safety and quality control applications. The company's products monitor air quality, temperature, and humidity in working environments; measure pollution conditions; detect gases and analyze gas pressure and temperature; and measure the flow rate of liquids. After an extended negotiation that started with a failed 1999 takeover bid, the company was acquired and taken private in 2000 by JJF Group, a private investment vehicle formed by former TSI chairman John Fauth (CEO of The Churchill Companies, which has bought about 30 companies since Fauth founded it in 1982).