either will go up if you have a fire and the fire gets close enough to them. the cardboard will burn up quicker and is less bug/rodent proof. the plastic will liquify and you will have flaming liquid dripping everywhere thus causing the fire to spread, but less chance of bugs/rodents getting inside.

neither will protect the stuff inside from fire, so i say go with the plastic for protection from critters.

my grandmother's house caught fire several years ago. all teh cardboard boxes in her attic were goners in no time, some before the fire itself actually got to them. remember the summer heat causes the cardboard to get super dry. there were a couple of plastic storage containers that only melted a little, the fire itself never got the to ignite them. but the contents of those was salvagable, whereas the contents of the cardboard boxes, even the ones not burnt, was not.

Cardboard is a poor storage choice for anything, really  itÂs flimsy to begin with, and degrades over time, especially in an environment where itÂs exposed to moisture, or heat, for a prolonged time. ItÂs also no barrier at all to critters, who think it makes excellent nest insulation.

Plastic burns ÂhotterÂ, yes  but it also has a higher flash point than cardboard, so is less likely TO burn  and provides at least some protection against smoke and water damage, which cardboard will not.

But the biggest advantage of plastic, for me, is the uniformity  I can easily stack four tubs by four different companies one on top of one another something I cannot do with four random cardboard boxes. This ability to get stuff organized, off the floor, and in neat stacks that arenÂt going to fall over because someone put a box of books on top of the summer bed linens is a much more effective Âsafety feature for me.

The biggest fire risk, after all, is a disorganized space.

chinacat, you bring up an excellent point that i missed. at work we store old records and stuff in the cardboard file storage boxes. a couple years ago one of those boxes fell thru the drop ceiling! the floor it was on is basically a ledge around 2 sides of the room, sticking out 4 ft fromteh wall and about a foot over the drop ceiling. someone piled the boxes up and set a full box on top of a partially filled box. a few weeks later the lower bow gave way and the full box fell right off the edge and to the floor below. in a house this would at minimum damage the sheetrock, or worst case it would bust all teh way thru.

Personally I would not be concerned about how it burns in a fire. Both will burn. It really makes no difference. Neither one will protect your items in a fire. The plastic might protect from smoke damage if the fire never actually reaches them. Use the one that stores you items the safest. Be more concerned about preventing the fire in the first place.

Also, not all attics are structured to deal with the heavy long term load of being "packed to the gills". If there is that much stuff in the attic, you might want to get the opinion of a stuctural P.E. to determine if the load is too much...or not.

speaking from experience and seeing what happened when we moved into my moms house after she died i would say cardboard is a definate no no. Mom had a cold celler filled from top to bottom with cardboard boxes containing fragile and antique ceramics, clothing that literally shredded as we took them out! The ceramics? we lost quite a bit of tehm do to bottoms falling out of the boxes.
we had to use hazmat suits to clean the cold cellar out due to black mold that was rampant through the cardboard boxes and clothing. (clothing and cardboard are a attractant to this type of mold)

Moms attic was also FULL of cardboard boxes full of iteems which stunk to high heaven due to dampness and we filled a 40 yd garbage container 4 times. We have been cleaning the house out and renovating since october and still we find issues that could have been avoided as a result of cardboard being used to store all of her 'treasures'. Luckily we are in the waste and recycling business so the garbage dumpsters are cheaper. Had mom listened to us over the years alot of the precious antiques could have been saved instead of ending up as landfill.

Being the neice of a fireman and a 5 times breast cancer survivor i can tell you this:
Plastic melts faster and hotter than cardboard does. BUT plastic containers are harder to ignite if stored the proper way. Cardboard will ignite extremely quickly and it only takes a spark. what does not ignite will mold. Many molds cause cancer of various types.

i hope this helps

Just a thought, do you really need all you are saving?

Worst fire hazard? Neighbors. Burned huge debris pile approx. 10' from our line. Legal to burn so close to the property line; I am addressing that with Board of Supervisors. We live on 6.3 acres but this was for his convenience to not have the fire directly behind his house (as in sight of?). Lit fire late Saturday; it was never "fully extinguished" as it should have been, but rather, left to burn out. Next day we had wind gusts of 50 mph (VA, 2/10 check it out); the winds re-ignited the fire. We had 3/4 acres of woods scorched. Fire within 40' of house. Neighbor was 'at the office.' I am more than grateful for good neighbors and our county Volunteer FD! Know your neighbors and their fire skills (or lack there of: "I didn't know it was going to be windy [i.e. didn't check weather report]; not attending or extinguishing the fire; no garden hose at the ready; no tools; close to wooded area). And if you have a volunteer FD, please support them!

A couple of other things to consider--cardboard attracts certain pests that feed on it.

Plastic, however, can be deadly if it's burning. My sister used to work in a home center, and at one seminar she attended, it was mentioned that in the event of a kitchen fire--given the amount of plastic most of us have in our kitchens--one would be dead from toxic fumes long before they'd be killed by the fire itself. I can't remember the exact length of time, but remember being shocked at the very short amount of time it would take for someone to succumb to the deadly fumes from burning plastic (seconds? a minute or two?) I remember thinking at the time, that there wouldn't be enough time for someone to escape.

What about well-sealed metal boxes?

I'd probable agree that cardboard is worse than clear plastic shoe boxes

Here is a link that might be useful: Clear Shoe Boxes

Definitely the toxic fumes from plastic are a worry, but agree cardboard isn't the best storage medium. If you are storing delicate items like artwork or photos etc, make sure the plastic is not PVC but polypropylene or something food-rated as the off-gassing the plastic gives off naturally will harm many materials.

I have heard attic storage is a great fire danger, especially with spontaneous combustion etc, which does require a little dampness etc. Conceivably plastic might be safer as it's impervious to water and bugs/vermin etc.