I carry the MicroShield on my key ring and have one in my pocket when on duty. I keep a Laerdal Pocket Mask in each of my various personal trauma kits. However, to date on all of my respiratory/cardiac arrests with one exception, I have only used a BVM or BV to ET. I have only had to perform CPR using mouth to mouth on one person and that was my mother (did not use a barrier device). Sorry I cannot be of help on this one. Pete