State of Decay: Year-One

Propane tanks can be found mostly in towns and farms across the map. Near the starting base (church) you can find one behind a gun shop. Make noise to attract some zombies and lure them to the propane tank.

Once you get some to follow you to the back, they are forced to stay close to the tank because the wall of the gun shop is blocking the way. Shoot it and you should get at least 3 since they are so close together.

If you have trouble getting this Achievement, use a Doll, Clock, Flares or Fireworks to lure zombies to the propane tank and then shoot it

There are a lot of propane tanks once you cross the bridge to the Fairfields however there are some scattered around in the towns and farms. There are 2 types of propane tanks, the small kinds that you would use for grilling and then the huge industrial size that is usually hooked up to a house or building.

Just shoot it once and it will blow up. Kill 3 zombies this way and the achievement is yours. Beware the splash radius!

This achievement can be unlocked very early in the game as early as the Prologue at the Ranger Station/camp site where you begin the game. Search around the camp sites and cabins like you're supposed to and you'll more than likely find a gun. If you don't happen to find one that's okay because you can just switch your character to Maya once you've investigated the gun shots and have met her. Once you've finished the Prologue and are tasked with leaving Mt. Tanner to find the church, you'll most likely leave by taking the truck located at the warehouse right by the Ranger Station. In here you will find a propane tank. As you're about to leave, several zombies will appear which is when you can knock this out. Just lure them close enough to the tank. This achievement is actually best done anytime you're alone further on in the game. Survivors you are with will always automatically attack zombies you're close to so if they are too close to the tank when you shoot it, they will be injured and lose a little trust in you. Even if they are at a safe distance where they won't be injured, they might lose some trust in you. At least that's what happened to me when I tried it a couple different times. Not a big deal though, and this early on in the game you can just start a new game if you choose to.