Really interesting concept. I like it. The sound is fantastic! There is some nice feedback when using the axe on zombies and on doors.
I agree that this game could benefit from some puzzles - like trying to minimize smoke getting into a room while trying to save stranded people. I think giving the npcs a health value of some sort that gets taken away from too much smoke inhalation or any other hazards would definitely make the game feel more tense... unless you already have that in there and I just didn't notice.
Using the item interface felt a bit clunky - I didn't like switching between mouse and keyboard whenever I opened the inventory. A hotkey for swapping between items like the axe and fire extinguisher would be welcome... again, unless this feature is already present and I just didn't realize it
Destroying the hint objects after reading them would also be welcome - maybe having a hint journal or some such thing in the inventory so you could access previously discovered hints and tutorials?
Overall great concept and with some spit and polish graphics wise (themed tilesets for levels would be cool, i.e. office building, warehouse, home, etc.) this game could really shine.
Thanks for the opportunity to play!