The health assessment data (originally done by Canadian officials) that accompanied the US approval for OAV specified at least a half-face mask with ACID GAS cartridges. Often acid gas canisters are combined organic vapor cartridges (both in a single cartridge) and that is fine.  But you cannot substitute single-type organic vapor cartridges. Goggles are also required.

OAV results in plume of acid crystals which will readily adhere to mucosal  tissues (including the conjunctiva), burning them.  Unlike particles in smoke they cannot be coughed out of your respiratory system.

I, too, often read of users who rely on "knowing which way the wind is blowing" to stay clear of the plume. But that isn't going to help you when the wind is absent, squirrely, or you have some type of malfunction.

Once I slipped on ice during a winter OAV session and accidentally yanked my wand partially out during a burn.  The pot of the wand was touching  the under surface of the combs. To avoid risk of a fire, the only solution was to yank the wand out into the open air immediately, even though it was at the height of the burn-off. Because I always wear my mask, I could do so with no personal risk.  In a few seconds, the emergency was over.

A mask with the proper cartridges costs about $35 and can be found on Amazon.  A high-quality wand (like a Varrox) plus mask, cartridges and goggles will cost about $200, all-in.  The material (OA) cost for the actual treatments is negligible, just pennies per treatment and the total annual per hive cost is probably less than 25 cents.  So the major expense is the one-time cost for the equipment. (Plus annual cartridge replacements for less than $20 if you use them a lot like I do.)  There are more expensive devices (around $400-500) if IIRC, that are considerably faster.  This would make a difference if you had several dozen to hundreds of colonies.  These still require the same personal protection equipment.

I do my own small yard of 14 colonies, and I do another 3 or 4 dozen colonies for other beekeepers,  in small yards of 1-8 colonies.  The Varrox is perfect for me. I usually have two colonies in process at once, staggering their start times, and it takes concentration to keep things running smoothly, but at a fast pace. I use separate sets of of timers for each colony. I have considered buyng a second wand to speed things up but I am not sure my brain could handle four timing sequences without making errors, even with timers.

Nancy

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