Foam makes a great home for ants.

They excavate galleries and set up house in the material.

You can put great stuff in the walls, just keep it out of the boxes.

Is there a problem with the foam expanding for a while after it's sprayed in? So you might over-spray and then have to whittle a bit off when it's dry.

You won't get electricuted. Of course, you won't be fixing the problem either. Ants aren't magically appearing at the outlet. If they are getting in, or living in, the walls, you should fix that problem before they cause real damage. Also, if you have a noticeable breeze running through the walls, that isn't good either. Is this an exterior wall? Is it insulated?

As for expanding, yes - it expands. You can trim it off with any saw blade or serrated knife.

Not seeing anything on the Great Stuff can itself regarding use in/on/near serious electron flow, nor anything in my DIY electrical wiring texts, I once conducted my own simple experiment, to wit:

The clear plastic nozzle/extension tube on my GS can was clogged with dried foam from a previous use (plumbing related). So I used a straight piece of coat hanger to push the dried "string" out of the plastic tube. (Came out easier than I expected, IIRC... so they picked the right plastic.)

I then LIT the "string" with a butane ciggy lighter... BURNED ALMOST LIKE A FUSE... maybe FASTER! =:O

I *never* again considered using Great Stuff near anything EE-lek-tri-kul. ;') Depending on the size/location/material that has the gap, I use either a portland cement based product, and/or the RED fireproof caulk NEC/NFPA approved for use in electrical apps.

I've been tempted to use anchoring epoxies, but they're not code-approved either, and turn to mush at only ~200-250degF.

I've generally filled the gaps around boxes with drywall mud, but can anyone see anything wrong with using silicone sealant?

I was correct--regular (beige) Great Stuff is NOT to be used to fill gaps and penetrations related to electrical work, gas/propane flues/chimneys, or any req'd firebreaks and draftstops... for that Dow has a REDish-ORANGE version which IS approved to stop the spread of fire, and drafts feeding a fire ("draftstopping", one word).

The gist of crosstalk on home inspectors' forums is that the "regular" expanding foams were failing NFPA fire-related safety tests left and right, so the mfrs. scrambled to come up with an ostensibly better (and more prominently dyed) foam.

No word on whether it's just as vulnerable to ants and other critters.

To me these expanding foams have been an "unprofessional" time-saving slap-dash device used by tract home builders who are cranking out the cracker boxes in the 'burbs... a scary realm where the tape-measure and a measure-of-diligence are unknown entities, and the recip saw is king... =:O But hey, time IS money, and firestop foam is WAY better than a big air gap.

Here is a link that might be useful: Dow Introduces Great Stuff Fireblock Insulating Foam

You are allowed to have minor gaps around boxes under the NEC, but I routinely fill them with EasySand20.

I think it would be better to fill these with a little sheetrock mud, but this will just fix the appearance you really should check into the ants and other ways to seal that breeze. Of course I'm sure the original poster is beyond all this now. As for Great Stuff, I caretake for a house in high wind conditions and sometime before I started there someone actually filled the inside of all the elec. boxes. Been that way over ten years and never caused any problems, other than changing faceplates cause they were all stuck. And I had friend who said even the fireblock kind is pretty flammable when dry.

"I was correct--regular (beige) Great Stuff is NOT to be used to fill gaps and penetrations related to electrical work, gas/propane flues/chimneys, or any req'd firebreaks and draftstops... for that Dow has a REDish-ORANGE version which IS approved to stop the spread of fire, and drafts feeding a fire ("draftstopping", one word). "

Trying to limit infiltration is not the same as draftstopping.

Sealing cable penetrations is not normally a draftstopping issue, but an infiltration issue.

Recently had occasion to try the Great Stuff Fireblock foam around a ceiling fan j-box, which had been loosened in its mount by the off-balance fan, chipping away chunks of the surrounding ceiling plaster in the process. Air infiltration from the attic space had become significant.

To stay on the foam topic, I will omit the highly NON-compliant slacker wiring found... and rectified.

Plaster of Paris? Joint compound? Probably better choices, but I had some turnaround time constraints... also had a free half-can of the orange GS on hand. Shake well, lol.

Anyway, GS/subtype-Orange did the job. Threatened to drip in few spots, but they cured into small stalactites, easily trimmed.

FIRE TESTING: After 36 hour cure, applied a butane lighter to a test blob, and Duh Orange Stuff burned AWAY, creating nasty (toxic?) black smoke in the process! i.e. it will NOT SUSTAIN a flame when butane flame removed (as observed with Regular Stuff), but it certainly doesn't strike me as much of a BARRIER to flame-spread in a house fire. This is a tad surprising, as it is expressly marketed as a substitute for the various (UL-listed?) RED caulks used by real sparkies.

On the plus side, the rim of foam that expanded below the level of the j-box, provided an outstanding "damping base mount" for the fan bracket, i.e. cushioned stand-off for both ceiling and box ears. Duh Orange Stuff is VERY resilient... at least in the short run. Coupled with my increasing skills in blade re-bending, that ceiling fan is now WAY "calmer", and can now run at its highest speed, w/out wobble or noise.