I got a smaller Sentry Fire safe at a garage sale I would guess around a year ago maybe more. I brought it home wiped the inside down and loaded it full of ammo for storage. I haven't opened it since. 

Today I opened it and the boxes all feel a bit damp and some have a slight white mold on them. The safe is not in a basement it's in my office and there is no way water got into it from the exterior.

I have another just like it I use for handgun storage that I open daily that doesn't have this issue.

Any ideas what caused this and how to prevent it? It's mostly 500 round cases still in corrugated cardboard boxes with a few bulk packs of .22 and a spam can of 7.62 R

7 minutes ago, brucin said:

Any ideas what caused this

Any possibility the boxes were damp when you put them in the safe?

7 minutes ago, brucin said:

and how to prevent it?

https://www.amazon.com/Dry-Premium-Quality-Indicating-Packets/dp/B00DYIVFGI/ref=sr_1_2_sspa?rps=1&ie=UTF8&qid=1541559058&sr=8-2-spons&keywords=silica%2Bjell%2Bpacks&refinements=p_85%3A2470955011&th=1

 

3 minutes ago, Sniper22 said:

Any possibility the boxes were damp when you put them in the safe?

https://www.amazon.com/Dry-Premium-Quality-Indicating-Packets/dp/B00DYIVFGI/ref=sr_1_2_sspa?rps=1&ie=UTF8&qid=1541559058&sr=8-2-spons&keywords=silica%2Bjell%2Bpacks&refinements=p_85%3A2470955011&th=1

 

Nothing was damp when I put it in. I'm really puzzled. Thanks for the link to the silica packs. I was going to look for them and you saved me the trouble.

I have owned a Sentry Safe for 10 years.  Originally purchased it from Home Depot or Costco.  Likely similiar to yours.

I strongly urge you to NOT store ammo or anything firearms related in it.   I believe the moisture comes from the fireproofing material that is in it's walls.  The constant humidity and associated smell is every bit the same today as when I first purchased it all those years ago.  I tried using trays of descicant, to no avail.  My safe is in my garage but I would not trust it even if it were inside my home.  When I first purchased it, I put the bolt from my 40 year old 22lr rifle in it.  Six months later it had a light coating of rust on it.  This was a bolt that never had a spot of rust on it ever.

I do not have room for a large gun safe.  What I have been using instead are several Fort Knox Pistol Boxes which are in several places inside my home.  Rock solid, not fireproof, no issues with humidity at all.  Btw, in addition to my handguns, I also keep the bolts from my rifles locked in them. 

Hope this helps,  regards.

13 minutes ago, oldguysrule649 said:

I have owned a Sentry Safe for 10 years.  Originally purchased it from Home Depot or Costco.  Likely similiar to yours.

I strongly urge you to NOT store ammo or anything firearms related in it.   I believe the moisture comes from the fireproofing material that is in it's walls.  The constant humidity and associated smell is every bit the same today as when I first purchased it all those years ago.  I tried using trays of descicant, to no avail.  My safe is in my garage but I would not trust it even if it were inside my home.  When I first purchased it, I put the bolt from my 40 year old 22lr rifle in it.  Six months later it had a light coating of rust on it.  This was a bolt that never had a spot of rust on it ever.

I do not have room for a large gun safe.  What I have been using instead are several Fort Knox Pistol Boxes which are in several places inside my home.  Rock solid, not fireproof, no issues with humidity at all.  Btw, in addition to my handguns, I also keep the bolts from my rifles locked in them. 

Hope this helps,  regards.

What I find really odd is the one that I open daily and keep open does not have this issue.

26 minutes ago, brucin said:

Nothing was damp when I put it in. I'm really puzzled. Thanks for the link to the silica packs. I was going to look for them and you saved me the trouble.

I gave a bunch of those to my son for his big safe. He says they work really well, inside is completely dry, and it's in his garage. Plus, when those packs get damp, you just pop them into the oven to "recharge" them.

11 minutes ago, brucin said:

What I find really odd is the one that I open daily and keep open does not have this issue.

I assume that is because the humidity does not have an opportunity to build up given you are airing it out frequently.

Btw, any papers I have in my safe that are not in sealed ziplock bags always feel moist and smell from being in the safe.   (Fortunately, paper does not rust, lol.).

I found it ironic that I had put my bolt in it for safekeeping but the safe itself turned out to be the biggest risk to it.

1 minute ago, oldguysrule649 said:

I assume that is because the humidity does not have an opportunity to build up given you are airing it out frequently.

Btw, any papers I have in my safe that are not in sealed ziplock bags always feel moist and smell from being in the safe.   (Fortunately, paper does not rust, lol.).

I found it ironic that I had put my bolt in it for safekeeping but the safe itself turned out to be the biggest risk to it.

I'm going to try those descant packs that Sniper22 recommended plus I'm going to open it much more frequently. The ammo looks good I opened a few boxes and nothing funny looking on the cases or bullets.