Protective effects of face masks have been studied extensively, but usually this involved personal respirators for professionals under idealized conditions, because of specific applications, for instance in military or occupational uses, involving protection of specifically trained personnel. This is different from deployment of masks in the general population during an outbreak of an infectious disease, where anyone may encounter the infectious micro-organism, implying much greater heterogeneity, in training levels (experience and understanding), goodness of fit of a mask, and activities interfering with mask use and thus reducing potential reduction of transmission. The protective effect of masks is created through a combined effect of the transmission blocking potential of the material, the fit and related air leakage of the mask, and the degree of adherence to proper wearing and disposal of masks. Personal respirators such as those worn by staff attending TB patients, are used primarily to protect the wearer, and are designed to fit to the face with as tight a seal as possible. Their efficiency is graded on the degree of protection the material offers, assuming a perfect fit and optimal compliance. In contrast, surgical masks, as commonly worn in the operating theatre, are primarily used to protect the environment from the respiratory droplets produced by the wearer. With these masks, facial fit is much looser. The fit of home made masks, which could be e.g. made of a tea cloth or other comparable material available in the home, is likely to be even looser. Thus personal respirators confer a higher degree of protection than surgical masks, and these are again likely to give a higher degree of protection than home-made masks. In professional situations, ample time might be available prior to use to ensure a perfect fit and to give extensive counselling on adherence, but it is unlikely this will apply to the general population in case of a pandemic. It is possible that the discomfort in wearing associated with a certain type of masks will lead to reduced adherence and thus to a loss in overall protectiveness [10, 11] . Indeed a review among health care workers could not determine whether personal respirators conferred better protection for the health care workers than surgical masks [10] .