Basics

This page aims to cover concerns with storing some materials/items in a Car or other vehicle that when parked (especially outdoors in a Parking Lot ) can get VERY hot
The page will then cover ways to find the information needed (if already published), the type of tests to do if the information is unknown, and finally ways to potentially address the issue.

Concerns

Aerosol Cans can rupture under high temperatures
Even if not causing Autoignition (especially if it is in a sealed container, and thus likely above the Upper Explosive Limit ), Temperature Swings can cause fuels and other similar substances to produce more pressure and vent said fumes where they would be in conditions more suitable to ignition/explosion (ie Outside of a Jerry Can and into the Automotive Winding )
Pyrophoric / Premixed Fuel - Oxidizer Materials present additional concerns
- Existing literature on transporting HazMat / Pyrotechnics may aid in this

Certain Medications (which one may want to keep in a First Aid Kit ) can degrade at higher temperatures
Documented Guidelines + Accelerated Aging are where these behaviors would be determined

Examples:
- Anti-Perspirant Deodorant wil often melt, and if inverted while this happens (due to being stowed loosely in a bag/backpack etc) it will resolidify OUTSIDE of the tube/in the cap, which also interferes with that screw-dispensing function
- Liquid Soaps / Gels will be less viscous. Not horrible, but changes pouring/dispensing behavior notably
- Phenomenon such as Chocolate Tempering (albeit similar, but even in other materials than chocolate)
Long term Thermal Cycling leading to chemical reactions that either degrade effectiveness, or even add novel hazards are another aspect to consider

Mainly relevant to OTS Products
Either find the SDS or MPS / read in a directions section
- Either lack of information (ie only what is LEGALLY required), or unclear information (Due to warnings being overly cautious and/or material composition being a Trade Secret etc, Lack of Testing can also occur, especially in mixtures)

Keep the Vehicle Cooler:
- Park in a Garage / in the shade
- Crack the Windows to allow SOME of the Hot Air to escape
  - Adds security concerns, and if it rains this could add issues although Window Deflectors could help prevent the latter
- Need to see if it exists OTS, but Solar Exhaust Fans or something akin to an adapted Start-Stop System / Remote Vehicle Starting but mainly for HVAC or Power Window operation could be implemented
Better Storage
- Storing Sensitive Items in the Right Orientation (Upright and Well Sealed etc)
- Storing Sensitive Items in the Shade/"Tucked Away"
- Using a Metallized Film or similar Radiative Heat Barrier to reduce heating by the sun
- Using a Cooler or similarly insulated box to delay the heat, preferably long enough to allow for the day/night temperature swings to calm the extreme and/or until a person uses the vehicle and it's HVAC system cools down the cabin etc
- Phase Change Materials around the item / in the Cooler (More Complex/Untested, but Passive)
- Active Storage in an Automotive Refrigerator / Freezer or Powered Cooler etc
Item Substitution
- Use Toothpaste Tablets and other Solid/Dry Options whenever possible