I have been using formic acid for several years but I would not use this
method since, in my opinion, it is too uncontrolled.  From Dr Medhat Nasr's
research presentations of his research, I understand that the concentration
of the formic acid fumes in the hive is quite critical. It must be strong
enough to kill the mites yet not strong enough to harm the bees.  Dr Medhat's
original work used an adsorbent medium (Homasote board) of a certain size
within a plastic bag with tiny holes (Ziploc's vegetable bag for fridge
storage).  Also important are: distances from frames and hive top; size and
placement of hive openings during treatment, ambient temperature outside
hive, and quantity of acid in the pad.  He has given out printed instructions
with dimensions for beekeepers to follow his work and there are pre made
products on the market.

I gather that a cheaper or less troublesome way of applying formic acid is
being sought and I do not doubt that these liners could be used as the
adsorbent medium to hold the acid.  However it would take much research and
sensitive equipment to determine how to achieve the required concentration
with them.

If of enough interest, I could dig out more information and references if of
interest and post to the list but it would be better coming from Dr Nasr
himself.  Alternatively you can e-mail me offline at [log in to unmask]
since I do make my own following Dr Medhat's original work.