Human Fall Flat

This video with narrated commentary will help you easily get all four achievements in the Factory level! Simply hit play and listen! If at any point you need a visual, you can check the video. Enjoy the video and happy hunting
This achievement starts at 12:24 in the video.

There are four items to throw into the fire:
A gold bar from the top shelf on the left as you enter the room
A lava-lamp-shaped item from the back left corner of the room
A valve wheel from the bottom shelf on the right side of the room
A gear from the top shelf of the table in the near right corner (the same shelf with the radio)

The radio does not need to go into the fire for this achievement.

I got on the shelves by simply climbing up the shorter shelves and wall climbing over to the shelves with the items, but you can also use the tall boxes that come out of the chutes to create extra platforms, if you don't like to climb along the walls.

Quoting planchetflaw 's comment: Grab the first and go left and hold it against the wall between the gold bar shelf and the climbable one. It will magnetised in place. Then continue doing that for the munitions (2 blocks), and then finalltly 3 blocks for the cog.

It's actually simple using those blocks and requires no proper platforming aside from simple jump grabs.

Starts at 13:08

Easy as it sounds, although platforming over the shelves can be tricky. However, the radio does not count and if you are trying to get “Radio Silence” then this will void the achievement. You must throw it off the edge of the level for that.