BACKGROUND : Infection occurs in 2-4% of arthroplasty cases, and identifying potential sources of infection can help to reduce infection rates. The aim of this study was to identify the impact and potential for the contamination of hands and gowns whilst scrubbing using sterile surgical helmet systems (SSHSs). METHODS : A colony-forming unit (cfu) is a pathogenic particle of 0.5-5 μm. Standard arthroplasty hoods and SSHSs, with and without the fan switched on, were tested for a 3-min exposure (to represent scrubbing time) on three subjects and a mannequin with concurrent particle counts and culture plates. RESULTS : All SSHSs were positive for Gram-positive cocci, with a mean colony count of 410 cfu/m2. Background counts were lower for laminar flow areas [mean 0.7 particles/m3; 95% confidence interval (CI) 0-1.4] than scrub areas (mean 131.5 particles/m3; 95% CI 123.5-137.9; P=0.0003). However, neither grew any bacteria with a 2-min exposure. The background count increased 3.7 times with the fan switched on (total P=0.004, cfu P=0.047), and all helmets had positive cultures (mean 36 cfu/m2). There were no positive cultures with the standard arthroplasty hood or the SSHS with the fan switched off. In laminar flow areas, all cultures were negative and particle counts were low. CONCLUSIONS : Sterile gloves and gowns can be contaminated when scrubbing with the SSHS fan switched on. It is recommended that the fan should remain switched off when scrubbing until the hood and gown are in place, ideally in a laminar flow environment.