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Working in Chemical Biological (CB) protective equipment causes thermoregulatory strain by restricting evaporative cooling. We quantified which impermeable ancillary items [gloves(G), body armour liner(BAL), respirator(R) and overboots(OB)] imposed the greatest and the least thermoregulatory strain through restricting evaporative cooling. The study was a five-condition repeated-measures design with male volunteers (n = 13) who stepped intermittently with recovery periods in a desert-like environment (40.5 degrees C, 20% rh). Conditions varied in the ensemble worn, with a matched weight secured to the area when an item was not worn: CON(CB suit plus all items), N-R(no R), N-BAL(no BAL [170g liner]), N-G(no G) and N-OB(no OB). The greatest reduction in thermoregulatory strain compared with CON occurred in N-G when the rise of rectal temperature was attenuated by 0.37 degrees C.hr(-1) (p < .001), extending tolerance time by 21.3% (p < .05) and improving perceived thermal comfort. The least improvement occurred for N-OB. It is recommended that the G permeability be examined further. Practitioner summary: Thermoregulatory strain was quantified when wearing impermeable protective equipment. The thermal burden of intermittent exercise in desert-like environments was best alleviated by removing gloves compared to removing a respirator, overboots or body armour liner. Reducing the evaporative resistance of materials used for such kit, particularly gloves, should be investigated.