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Diagram of search strategy results and article selection for three searches. 1Includes 3 papers that were sought for review and abstraction in the first search. 2Includes 6 papers that were sought for review and abstraction in the second search. 3One of these papers (reference no. 6) became available on‐line on 27 January 2011. 4Reasons for exclusion included an inability to distinguish the effect of mask use from other personal protective equipment or lack of quantitative data.
