Does sulphur dioxide on the surface of a bag or box degrade over time?

Can anyone advise whether possible sulphur dioxide left on the surface of a bag or box following sausage manufacture degrades overtime and whether sulphur dioxide degrades further on the surface of a bag or box containing sausage which has been frozen.

Thanks 

No direct experience of the product, and there will be many variables, but in general yes I'd expect SO₂ to naturally degrade over time to some degree. I'd also expect that effect to lessen in frozen storage, as the lower temperature will reduce the rate at which most types of chemical reaction occur.

It's difficult to provide anything quantitative on this as it will very much depend on the environment to which the SO₂ is exposed, although I'm curious to know the context of the query ;)

Sulphite residues ?

SO₂ per se "tends" to be a gas albeit existable in liquid equilibria.

We are trying to validate a process to ensure that there are no sulphite residues/sulphur dioxide left which could cause cross contamination.

Without giving too much confidential information away, Raw Sausage containing the allergen sulphites, are packed into boxes.  The boxes are frozen down by placing the boxes in the freezer.  The next day when some the contents are still partly frozen, some of the boxes are opened and then placed in food grade bags.  We are assuming that there could be allergenic material on the outside of the bags & boxes (yet to be confirmed)

We have been carrying out trials on the frozen boxes & bags a few days later to pass them  though a metal detector in another area of the factory and so far all swabs taken came back as <10 Sulphur Dioxide which is what the lab uses to measure sulphite residues.

Just wondering if sulphite degrade over time and also with being in a frozen environment.

Any information welcome as to how sulphites behave 

In ambient products in a product matrix it is expected that sulphite levels will generally decline over time, as these will interact with component parts of the product (or products of other interactions in which parts of the product are present) and this is how sulphites serve a "useful" function - there is of course the microbiological preservative element, but e.g. in wine there is also a more general preservative effect, spanning everything from enzymes to oxidation events that would otherwise generate off-notes. It's fairly complex chemistry in some senses, as there is a great deal going on.

Exactly what the behaviour would be on the surface of a packaging product is not something I've seen any data on, and in any case I'd expect it to be very specific to the "product" matrix, whatever that may be - some moisture and possibly a bit of residue of the meat product? 

I'd expect that temperature will also be difficult to account for, as whilst it's generally a safe assumption that most types of reaction will slow down at lower temperatures (as a lower temperature basically means there is less energy in the system), the exact effect could be expected to be dependent on the specifics of the reactions that are occurring.

You know your product and process best, but at face value I'd be reticent to rely on any depletion of sulphite content in this way as any sort of control measure, particularly over such a short timescale - consider that some products in which sulphites are supposed to provide a technological function rely on them lasting for months/years even at ambient temperatures.

I think in your position I'd start by looking at the levels on the outside of the boxes immediately after packing them, and taking that as the effective level present for the purposes of planning how to handle/control the potential risks.