You haven't mentioned if these are neat or diluted acids nor what ambient temperatures they are used in:

SDS Section 2 Classification covers the product as supplied

SDS Section 3 lists the component substance(s) as 100% w/w

Looking at the SDS posted by a major on-line reagent seller in Section 9 we have:

Flash Point 49 C, Flamability Limts 38 > 18% for <100% w/w Formic Acid

Flash Point 39 C, Flamability Limits 19 > 4% for <100% w/w Acetic Acid

Then no surprise in Section 7 Storage class (TRGS 510 - German rules): 3: Flammable liquids

Based upon the above I think you will find your insurers would expect to find these in flammable cabinets.

Not sure if they still supply materials this way anymore but we used to keep our 2.5 Litre Winchesters of Acetic Acid in their plastic screw cap shipping case inside the flammable cabinet.

Thank you for the information.

The acids are both dilute and stored in ambient temperatures (around 21 C)

I have been finding it hard to get guidance on this. We currently have these in a flammable cabinet, but as a corrosive, it is causing cabinet components to rust, such as the locking mechanism. The current flammables cabinet is not actively vented. Perhaps having the fumes actively vented would prevent build-up and rusting.

Acetic Acid 60% solution (or less) is not classified as a flammable product in Section 2 of the SDS which shows Skin Corr. 1B - H314 & Serious eye damage Cat. 1 - H318

H226 is still present in the substance as 100% w/w displayed in Section 3 but this is not the classification of the supplied product.

People might be getting flashpoint mixed up with autoignition temperature. Neither of these products is flammable ie with a flashpoint at or below room temperature (23 °C) and as they are diluted I am not sure they even count as combustible. My concern would be with their corrosive character and that they give off  fumes when you spill them.  Do you have a spills procedure and do you access to PPE especially  for the formic acid?  

Rather than the specifics the following applies.

• For storage, the flammable properties take priority over the corrosive properties.
• To be classified as flammable, under the current classification system you need a flashpoint of 60oC or below - that's why diesel is now classified as flammable.
• Flammable cabinets used in internal areas should not be vented. They are required to be 30 minutes fire protected and clearly, vents don't allow for this. External flammable cabinets can be vented, but these need to be suitably located.

Hope it helps,

Tony.

Edited by user 28 July 2023 07:36:53(UTC)  | Reason: clarification added.