My apologies for the fire references, but Life Happens.
My storage is practical. After helping to clean out my mother's house after a whole house fire, and then many years later, my own, I learned several very basic, but important facts.
Metal warps, and even melts. A whole house fire is incredibly hot. Metals run and pool like water. Plastic melts. Plastic bags melt and dissolve into hot droplets that are toxic and that eat even tintypes. The plastic hangers in your closets will dissolve and drip on anything below them. The top shelves in closets are miniature ovens and all there will be ash. Your computer equipment will be eaten by the fire, and if it survives by odd circumstance as mine in the basement did, it will eat itself slowly but surely, due to the chemicals added to the fire hose water that help to stop the fire.
The safest place for any storage of critical documents is in a tight fitting, tight closing wood chest or drawers. The wood swells when the firemen shoot water into the house, creating sealed storage. The wood needs to be actual lumber made, not laminated wood that warps and has glue that will dissolve or create fumes. The fumes eat your photos and papers.
The wood should be close to 1 inch or 3 cm thick. Hardwood if possible.
I had purchased 3 or 4 second hand college dorm desks from a University, and my children used them. I stored photos in the bottom drawer of mine, in my kitchen. Those desks were thick, and designed to take generations of college students abusing them. The documents and photos inside the solid wood drawers at the lowest level survived the fire that even melted the cast iron cookware in the same room.
Just as had happened at my mother's, anything in the open, in closets, and above 2 feet above the floor was forever burned, and in ashes. Anything within 2 feet of the floor, but raised at least 3 inches / 10 cm survived both the fire and the flood of water.
Waxed wood works better than lacquered.
If the document, photo, or item is important to you or your family, then treat it with the care it deserves.
Nothing plastic, synthetic or metal will survive a fire unscathed. Thick hard wood is stronger than steel, longer lasting, and safer. If an item needs more protection, place it in a tight fitting wood box within the wood chest. Metal safes pop open in a whole house fire.
If you store in a concrete room, be sure it is truly sealed, with a tight fitting solid wood door. and above the outside water table. The water from the fire hoses will go down into any basement or cellar.
And lastly, use only acid free paper between photos. The old fashioned true acid free black album paper or artist grade acid free paper work well.
I am actually looking for old library card catalogs, and more of the birch university desks. If I am lucky enough to find them, I will, with great love, find a spot in my home, and my photos will once again be safe. Until then, they are in the thickest wood chest I have.
We were lucky enough to survive, and the whole family got out. Everything else is second. I can honestly tell you I didn't cry over the house. I didn't cry over the furniture or electronics. I cried over loosing the small keepsakes from my parents, and over loosing more than half of my family's photos from over 150 years. And yes, I admit it, I cried that the handwritten notes in the family bible were gone forever, as well as the Senteney Haney Reunion notebook with over 150 years of notes.
So, Take digital photos of the photos, scan them, share them, post them on web pages and pass on their history with Joy. Life Happens! But if you need to save them, store them in thick hardwood, and forget the plastic.