The following is an artical by Michael Bain, Zinpro Country Manager

Fact One: formaldehyde is indeed sensitive to cold conditions.

If it freezes or is exposed / stored mid to long term in cold conditions (i.e. below 15 C / 60 F) it definitely can polymerize / precipitate into para-formaldehyde that makes the product less or no longer active. Some labels actually specify this.

Presence of methanol definitely helps preventing this from occurring but some commercial products contain less methanol than others and are thus more sensitive to cold conditions. Industrial formaldehyde might not contain methanol at all!

Fact Two: although diluted solutions are used in foot baths, sprayed or fumigated and may not freeze they have a low risk of polymerization (obviously, a 2 - 3 % solution kept only for a short period of time is not as prone to polymerization as the 37 % product in the jug), formaldehyde is nonetheless still sensitive to cold conditions and is well known to lose some of its efficacy as the temperature decreases, contrary to some other disinfectant families!

So, the colder the conditions, the less efficient the solution becomes.

In North-America, approved commercial disinfectants are normally only tested at 20 C / 68 F, and no one really knows for sure how efficient they are in colder conditions because they simply were never tested in colder conditions. This explains why many labels specify that room and surfaces should be at least 18 C / 65 F in order to achieve best results when the solution is sprayed or fogged. This would also definitely apply to a solution used for footbaths over a few days.

So, would a 2 - 3 % solution of formaldehyde still be efficient at around 7 C / 45 F or below?

Maybe not!

Michael Bain, Zinpro Country Manager