This achievement takes place over two chapters, Sundown and Nightfall. Phoenix0689 has covered the two Nightfall locations above, I will concentrate on the Sundown locations I've discovered so far.
Where you first start the chapter there is a box with an incendiary grenade, air filter and medkit.
After walking down from the start head to your right, cross the marsh through the red safe crossing flags. There is a white ruined building by the edge of the marsh, on it's ar left side there is a red box with grenades, shotgun ammo and a medkit. (Caution there is a demon feeding on a corpse, the corpse has few shotgun ammo rounds. Not sure if this is needed or achievement)
Go back to the red flags you just crossed and turn right, there will be a space in a wall, this is a mini storage facility that is separated by the marsh. This section has a white moving semi truck. Go around the truck, squeezing between it and the wall to the rear. In the corner at the end of the truck is a corpse with ammo and a mask. The back door of the semi is open, cut the tripwire on the left side by the jug, inside the red ammo box are incendiary grenades.
Go back around and to your right you will see another set of red flags that will lead you to the other side of the facility. At the first flag there is a corpse with shotgun ammo. After crossing, there will be two rows of storage units. on the right side will be one that is blocked by a car. Go around the car and cut the tripwire on the right side by the jug. Inside the storage unit there is a lamp, ammo box and pistol. After leaving this unit stay on that same row of units and there will be a corpse with a mask and shotgun ammo to loot. Turn around and you will see a sniper tower, go up the stairs and you will find a sniper, ammo and mask.
From the sniper tower, go down the stairs and walk straight out through the facility front gate and turn right. A few steps further a doorway to a ruined building, after walking through turn right, in the back of this room is an animated corpse with an air filter. After looting turn around, without walking, and face in the direction of the door you just came in through, on the left there is an opening, walk through this opening and on the left again their is another opening, after walking through to the let their is a mask and claymore. After picking this loot up, turn around and walking toward the marsh and turn right at the end of the ruined building, on your right, two rooms over is a sleeping armored shrimp, kill him and there will be two corpses with a shotgun and ammo. Turn again and walk toward the swamp and turn right and walk to the corner of the ruined building. From here you can see a red crossing flag and a retail center.
After crossing over the red lags there will be two rows of retail stores and in between the rows will be vines with tentacle monsters that will swipe at you. Trying ducking when in these areas moving from room to room. Walk over to the farthest and longest row of shops where the brown tractor trailer is. In this first shop there will be some incendiary grenades. After looting leave this shop while ducking and turn left. Ignore the next shop and go to the third one, here and the door will me a corpse with ammo, mask and medkit, further inside is mask and a grenade on the shelf. Leave the shop while ducking, turn left. The next shop also has grenades on the shelf. Next proceed to the last shop that has a tripwire on a hole for an entrance. Cut the tripwire to the let of the door entrance. Inside there is a Kalash 2012, ammo and a claymore to loot. Leave this room and turn left a few steps forward you will see red flags that will lead you toward the gas station.
After crossing you will see a tanker and delivery truck. Inside the delivery truck is a mask and air filter. Walking out of the delivery truck to the left is the gas station. Beware the tentacles at the front door. Inside to the left in the corner is a BIG ammo box, next to are the fuel cans. On the front counter, opposite the gas is a diary page, throwing knives and ammo. Leaving the gas station through the blown out back wall you a warped steal beam leading to the roof of the gas station, on top is a backpack with grenades and a corpse with ammo, Go back to the warped beam, jump down and you will see a log to cross over to a torn down building there is a mask and ammo in front of the blue bus on a corpse. Behind the bus are a set of flags leading to the airplane where there is a corpse to loot on the way.
To the right of the airplane door are some claymores. To the back is a lamp, big ammo box with mask and filter. To the right of the ammo box is a medkit and ammo also. After picking up the gas cans there is a cut scene. DON'T WASTE YOUR GRENADES. Leave through the plane door, turn right up the plane wing and jump off the opposite plane wing to find a box of shotgun ammo. Looking back toward the plain to the right are planks of wood where you can run jump over the marsh toward the plane.
From hear cross the series of red flags back to the bus. Use the compass to direct you to the ferry crossing. At the ferry switch there is an ammo box and claymores. The tree next to the ferry switch has a corpse with an air filter. There is also a corpse at the end of the ferry dock.
Things to remember, Sundown is a good place to get the SOUP and DIVER achievements. I also noticed that you can actually lose air filter time if you switch masks, so be on the look out when trying to loot and accidentally switch mask.