If the three groups are given different types of masks it's hardly double blind, is it? It's not even single blind.
The masks would look and feel identical. Not impossible to do, by any means.
To ensure the masks were used appropriately, participants would be instructed on their use. To keep it blind, there would also be 3 groups of instructors.
@Eseman started
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If the three groups are given different types of masks it's hardly double blind, is it? It's not even single blind.