On 11 June 2009, the World Health Organisation (WHO) raised the influenza pandemic alert to Level 6 (defined as ‘sustained community level outbreaks in at least one other country in another WHO region’) because of the emergence of a novel influenza A/H1N1 subtype. 1 Australia’s first laboratory confirmed case of pandemic (H1N1) 2009 virus, a NSW woman who had visited Los Angeles, was reported in the second week of May 2009. The National Institute for Occupational Safety and Health (NIOSH) regulates the testing and certification of respiratory protection equipment. 2 The NIOSH tests filters for the effects of loading (particle burden), temperature, and relative humidity and requires a minimum filtration efficiency of 95%, 99% or 99·97% using neutralized 0·075‐mm count median diameter solid aerosols at 85 l/min. Jefferson and colleagues concluded that more experimental studies were needed to identify the effectiveness of wearing face masks or respirators in reducing exhaled infectious viral particles. 7 In 2009, we reported the first prospective cluster‐randomized trial comparing surgical masks, non‐fit‐tested P2 masks (N95 equivalent) and no masks in prevention of influenza‐like illness (ILI) in households. 10 Intention to treat analysis showed no significant difference in the relative risk of ILI in the mask groups compared with the control group.