[Idiom] "Hard hats must be worn at all times"

I'm a Engilish-Japanese translator.
Please tell me the meaning of the following phrase: "Hard hats must be worn at all times".

[Soup]

Hard hat <See picture here>
must <necessity>
worn <past participle of wear>
must be worn <passive; active: you must wear (your hard hat)>
at all times <all the time [while in the hard hat area], every minute>

あなたのヘルメットをいつも身に着けなさい
あなたのヘルメットをいつも身に着けなければならない

[konungursvia]

It comes from the 安全第一 information campaign for construction sites, meaning "You always must wear a very hard plastic yellow hat for safety."