If you've cited a yard for an oversized tire pile and then walked past a scrap metal mountain twice the size without writing a word, you're not being inconsistent. The code treats the two materials differently on purpose, and knowing why makes the walk-through faster and the citation harder to argue with.
Why tire piles draw tighter limits
Scrap tires burn in a way almost nothing else on a yard does. They don't just ignite, they smolder deep inside the pile where there's no airflow, they produce pyrolytic oil that pools and re-ignites, and a pile that looks out once can keep burning underground for weeks. That's the fire behavior NFPA 1's outdoor scrap tire storage provisions are written around, and it's why the code doesn't just say "keep it contained." It regulates pile dimensions, the clear access lanes between piles, and setback from property lines and exposures, because the goal isn't stopping ignition. It's making sure one pile catching doesn't take the whole row with it, and that an engine can actually get a line between piles once it does.
This is also why tire storage limits get enforced as a hard trigger rather than a judgment call. A pile that's grown past its footprint or crept into the required access lane is a code violation on its face, whatever the yard's excuse. The specific height and area numbers come out of your adopted edition of NFPA 1 and whatever your local fire marshal has layered on top, so that's the first thing to confirm before you write anything up. What matters on site is whether the pile matches the dimensions on the permit.
Where scrap metal piles get judged differently
Scrap metal, especially clean ferrous, doesn't carry the same combustion risk, and most fire codes reflect that by regulating it more loosely. A baled or shredded steel pile burns out fast and doesn't smolder for weeks the way a tire pile does. That's why a scrap metal stockpile can dwarf the tire pile sitting next to it and still draw no finding, as long as it's inert.
The catch is that "inert" is doing a lot of work in that sentence. Automotive shredder residue, insulated wire, and ferrous scrap still carrying oil, fuel, or upholstery foam all bring combustible fuel load back into the picture, and plenty of facilities store those fractions right alongside clean metal without separating them on paper the way they're separated on the ground. When you're checking a scrap yard against its fire code storage conditions, the question isn't just pile size, it's composition. A permit written for clean scrap doesn't cover a pile that's been picking up ASR fines over a few months of steady intake, and that's usually the gap worth checking first, not the height of the metal pile itself.
Checking both without a full walk-through
Pile dimensions change month to month, and most inspectors can't get boots on every parcel on a schedule tight enough to catch drift before it becomes a violation. A tire pile that was within its footprint at your last visit can grow past the access lane setback in a few weeks of steady intake. A scrap pile that was clean metal in spring can pick up a contaminated load by fall with nobody flagging it.
That's the gap Recycling Facility Map is built around: a monthly count and volume estimate for what's stored on site, read from overhead imagery, so you can see which piles have grown past what the permit allows before you schedule the drive out. It won't tell you what's mixed into a pile, but it will tell you where the footprint and volume have moved, which is usually the first sign something's worth a closer look.
If you're cross-checking storage against a facility's permit on a recurring basis, that's the use case this is built for.