A study was undertaken to investigate the effect of changing the geometry of a bench scale tester from planar to cylindrical on the thermal protective properties of single-layer fabrics. The design of a cylindrical geometry tester is discussed in detail. Its size was selected so that it can be a direct replacement for presently used planar geometry units. Like planar geometry testers, the cylindrical unit can be operated with or without an air gap between the fabric and the sensor. Results are presented only for the case with a 6.35 mm (1/4 in.) air gap. They show that fabrics which shrink during the test can have reduced thermal protective qualities compared with the performance measured with a planar geometry tester.