apiguard reaction

Like to know what type of mask to use when working with Apiguard. Although I have been working with it without a mask, I noticed that it is an irritant and would like to know if there is a mask suitable for this.

This is my first year with bees and today round 4 I put apiguard in my two hives, went to store. Came back and walked over to hives and they were covered with bees, and the air is full of bees. Is this normal? If not, what went wrong, if something is wrong. Both hives are acting the same way...