When pulling up particleboard underlayment, it's easier to take it up intact. Here's my method. I walk around on knee pads, with a cat's paw nail puller, I drive it under the head of a nail with one blow of the hammer, a helper pushes the puller with his foot, leaving the nail head above the floor. When I get tired of being on my knees, using long wrecking bars, so we don't have to bend over, we go around, and pull the nails all the way out, dropping them on the floor. Once all the nails are out, a magnetic sweeper picks them all up, and drops them in a tossable container (junk cardboard box).
With all of the nails out, a flat bar to start the first edge up, and then it all comes right up, to be carried out in the minimum number of pieces. It really goes along fairly quickly.
The nail puller is pushed by a foot because it gets to be a tiring, odd motion for an arm with many repetition. Limit footsteps, and limit bending over.
edited to add: My Pulling toolbox weighs about 65 pounds, and it doesn't hold the stuff that's longer than 28". For particleboard, the blue, sharp, pointy ended Vaughn pullers would be my first choice. You can find them in a number of sizes in Lowes. You want the smallest end, that will go down in the particleboard the easiest, and still have a big enough slot to hold the nail, under the head. The big, wide headed ones will be much harder to drive down into the particleboard.
https://www.amazon.com/Vaughan-Bushn.../dp/B00004Z2WK