I had a bottle of 100 mg VG-nic that had almost zero headroom stored in the freezer. I use 50 mL amber glass bottles from SpecialtyBottles.com, the kind with the eurodropper inserts. These inserts act as a sort of septum, where the liquid can be syringe-dispensed through the eurodropper center hole, but they make the bottle completely spill-proof. In fact, I use these with almost all of my DIY liquids, from water to VG to flavors to nic. I use syringes for all DIY liquids. But I digress...
The bottle sealed and was sitting on the desk in my office, which was around 90 F degrees. After about 1/2 hour, I noticed that the liquid was starting to leak out from under the lid. I had processed the nic for storage in my kitchen in the winter time, and my kitchen was fairly cold (~60 F) at the time. Evidently the liquid had contracted a bit in my cold kitchen, and expended a bit at higher temps after I had brought it out of the freezer.
Spill a good amount of 100 mg onto the floor or into a carpet, and yes, you have a serious hazmat emergency, which will require professional remediation. There used to be a hazmat technician here who described what would be needed for such a situation, like spilling 200 mL of 100 mg liquid. The house or apartment would likely be condemned, the carpet would be removed and incinerated. Full suits and respirators. Not good. Anything that avoids spills, like septa or eurodropper inserts will virtually remove that risk. Glass bottles for chemicals, especially when sealed, are fairly resilient to breakage, but of course it is still a risk. Spills are far more easy to have happen if it is just an open bottle...and you've been vaping a lot of nic!