KEY WORDS: Related to masks: masks, respirators, face coverings, non-pharmaceutical interventions (NPIs), respiratory protective devices. Related to mask mandates: mask mandate, face covering mandate, mask regulation, mask policy. Related to respiratory outbreaks: respiratory outbreak, respiratory pandemic, epidemic control, public health intervention, Specific respiratory illness keywords: COVID-19, SARS-CoV-2, influenza, SARS (Severe Acute Respiratory Syndrome), MERS (Middle East Respiratory Syndrome). Policy and implementation keywords: mandate effectiveness, compliance, enforcement, policy analysis, implementation study, legal aspects, public policy. Outcome and Effect Keywords: transmission rate, infection rate, disease spread, hospitalization rate, mortality rate, community transmission, effectiveness, impact, efficacy. Mechanism keywords: social norms, behavioural science, public perception, risk perception, compliance behaviour, altruism, social psychology. DATABASE SEARCH STRATEGIES: Combine keywords using Boolean operators (AND, OR, NOT). Example: (mask mandate OR face mask policy) AND (COVID-19 OR influenza) AND transmission rate Use truncation (*) to capture variations of words. Example: mandate* will find mandates, mandated, etc. Use phrase searching (quotation marks) to find exact phrases. Example: "public health intervention". Use MeSH terms (Medical Subject Headings) in PubMed/MEDLINE. Example: masks, respiratory protective devices. EXAMPLE SEARCH STRINGS: PubMed: (mask mandate[Title/Abstract] OR face covering mandate[Title/Abstract]) AND (COVID-19[MeSH Terms] OR influenza[MeSH Terms]) AND (transmission[Title/Abstract] OR infection[Title/Abstract]). Google Scholar: mask mandate AND (respiratory outbreak OR pandemic) AND (transmission OR effectiveness). These keywords and search strategies will be piloted in the specific databases and modified in response to emerging findings.