From the UESP Wiki, "Containers - Safe Containers":
Containers may be safe for one of two reasons. Some container types
are set to be non-respawning — containers of that type will never
respawn, no matter where the container is found. Other containers are
safe because of their location — some locations, in particular the
player's houses, are identified as non-respawning locations. All
containers in these safe locations (even common Barrels and Sacks) can
safely be used for storage.
The ff. are safe containers for storage:
- Child's Chest - a part of child's bedroom [Hearthfire DLC]. It will be empty if you haven't adopted any children. Your children may collect various things and store them in their chest. Their older weapons, clothes and dolls will be kept in it too, if you give them a new one. Your children will restock it every few days. However, the original contents in it won't disappear.
- Coffin - found in Halls of the Dead and Vampire Dungeons
- Cupboard - common furniture in houses
- Dresser
- End Table - most frequently seen in houses
- Pot
- Riekling Hut [Dragonborn DLC]
- Strongbox
- Wardrobe
From the UESP wiki's "Containers - Safe Locations" article:
Safe locations are places that never respawn. Therefore, every
container in the location (even a common barrel or sack) is safe for
storage. The primary example of a safe location is a player-owned
house, but a large number of other places are also
non-respawning. Unless noted otherwise on the place page, only the
interior areas of these locations are safe — i.e., only regions that
are entered through a door that triggers a loading screen, and have
their own map, separate from the exterior map.
In a few instances, there may be quest-related changes to the location
(as noted on the individual place page), but otherwise the game does
not modify the contents of a safe location.
The following are safe locations for storage (from the UESP Wiki):
These are places that never respawn, and therefore none of the
containers automatically reset. Any quest-related changes to the
location are noted on the place page. Note that individual containers
in other locations may also be safe for storage.
- Abandoned House
- Angarvunde
- Angi's Camp
- Anise's Cabin
- Arkngthamz
- Avanchnzel
- Blind Cliff Cave
- Breezehome
- Broken Oar Grotto
- Bthardamz
- Calcelmo's Laboratory, Understone Keep
- Calcelmo's Tower, Understone Keep
- Cracked Tusk Keep
- Dark Brotherhood Sanctuary
- Darklight Tower
- Dawnstar Sanctuary
- Dimhollow Crypt
- Dustman's Cairn
- Dwemer Museum, Understone Keep
- Forebears' Holdout
- Froki's Shack
- Frostmere Crypt
- Geirmund's Hall
- Glenmoril Coven
- Goldenglow Estate
- Harmugstahl
- Helgen
- Helgen Keep
- Heljarchen Hall
- Hillgrund's Tomb
- Hjerim
- Honeyside
- Inner Sanctum (Vale)
- Irkngthand
- Ironbind Barrow
- Japhet's Folly
- The Karthspire
- The Katariah
- Korvanjund
- Labyrinthian
- Lakeview Manor
- The Midden
- Mistwatch
- Mzulft
- Nightcaller Temple
- Nightingale Hall
- Nilheim
- Northwatch Keep
- Potema's Catacombs
- Proudspire Manor
- The Ragged Flagon
- Ragnvald
- Rannveig's Fast
- Reachcliff Cave
- Reachwater Rock
- Ruunvald Excavation
- Saarthal
- Sea Cave
- Sinderion's Field Laboratory
- Snow Veil Sanctum
- Southfringe Sanctum
- Statue to Meridia
- Stillborn Cave
- Tower of Mzark
- Ustengrav
- Valthume
- Vlindrel Hall
- Windstad Manor
- Wreck of the Icerunner
- Yngol Barrow
- Yngvild
- Ysgramor's Tomb