Question

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Why do policemen regulating traffic at a crowded crossing often wear a mask?

Answer 1

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Wearing a mask at a crowded crossing saves the policemen from harmful smoke and dust particles emitted by vehicles, which may enter their nose.