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Comment by sn_master | Hacker News Reader

Polyethylene is highly flammable. The article isn't talking about how they're solving this (are they?).

This has been a problem for quite sometime now, with many high-profile cases (https://www.bbc.com/news/uk-41680157).

This was an excellent ABC documentary I saw sometime ago on the same topic: https://www.youtube.com/watch?v=gnTZLzXq8fU

Wood also is highly flammable and that is not stopping one of the most developed country in the world to keep using it to build houses.

It doesn't melt though. In fact mass timber is relatively resistant to fire, possibly better than steel. If I remember correctly, the surface chars and becomes a relatively good insulator of heat, so the core preserves its strength.

Wood really isn't that flammable either. Most thing in your house, furniture, paint, books, drapes etc. is on fire before your walls or your floor. Huge caveat on solid wood walls and floor.

Wood used for construction is required by law to be fire treated.

https://www.fp-supply.com/st-louis-fire-treated-lumber.html

Where? In what contexts? It's not required for houses or town houses where I'm from at least. From the pictures I guess it's mostly relevant to larger buildings?

"Over 90% of the homes that are built in the United States each year are constructed using wood-frame construction"

https://awc.org/codes-standards/firesafety

And close to 100% of those are built with garden variety untreated fir lumber.

This is too general a blanket statement to be true. Plenty of wood in construction is not treated for fire. Fire ratings are generally done for assemblies, not components of assemblies, and there are ways to build fire rated assemblies without treated wood. Also, not all assemblies need fire ratings. Sometimes its just the exterior walls adjacent to neighbouring structures, etc.

wood is a lot less flammable than a material made of chains of hydrocarbons, and has far preferable burning characteristics to plastic.

The two facts that 1) you could burn wood and 2) people build with wood, should not logically lead someone to claim that building things with any flammable materials is ok because of this.

These are mostly used for paving stones (or at least they were when I met Nzambi a couple years ago), so the flammability issue is not as much of a concern since they are not inside buildings but rather used for walkways usually placed in the dirt.

I could totally imagine a walkway made of polyethylene blocks could catch fire in a big way... You wouldn't want that walkway to be all around your house...

FTA

"These are high density polyethylene, used in milk and shampoo bottles; low density polyethylene, often used for bags for cerals or sandwiches; and polypropylene, used for ropes, flip-top lids and buckets."

Are cereal bags, ropes, shampoo bottles and buckets highly flammable?

Yes?

https://www.sciencedirect.com/science/article/abs/pii/004060...

If you have a counter-source, please share it.

I don't, I was genuinely asking. It would seem like given it's popularity that would be an issue. But, crazier things have happened when it comes to consumer safety regulations.

Anecdotally I've probably touched an open flame to synthetic rope, milk jugs and maybe a bucket or two in my life but can't say I've ever seen any of these items react in an uncontrolled or dangerous way.

Sure, they're flammable.

But the amount of BTUs in, say, packaging, is negligible, because it's so lightweight.

When you combine lots of recycled packaging into dense bricks, it becomes a lot of dense BTUs, so can provide a lot of fuel to a fire.

Plastic fires are nasty. Aside from toxic fumes, plastic melts, So gravity will help it spread, if there's a way for it to do so.

You're not going to cause a runaway with a lighter and a pop bottle without working at it. But, say, an electrical short in a closet with hanging synthetics can take off pretty quickly.

And of top of that, burns from plastics are HORRIBLE, think napalm, but worse.

In a college engineering class we produced (in teams) rockets emitting mach-diamond exhaust consisting of nothing more than HDPE rods bored in specific patterns, supplied with pure oxygen, and ignited.

> supplied with pure oxygen

That is key. A lot of things make a hell of a flame when you supply them with pure oxygen.

A thermic lance is a steel tube with pure oxygen fed down the bore. Here's how to make one out of a length of automotive brake line. https://youtu.be/EA-VCaBUsCA

I would imagine the mixing in of sand would mitigate this mostly.

I would love to see how that works. The ABC documentary is saying that even the big-industry produced polyethylene for buildings isn't properly flame-resistant, even the EU-approved ones.

There was a Reddit thread where someone made a case why it wouldn't:

https://www.reddit.com/r/worldnews/comments/ler5uc/kenyan_re...

I'm certainly not an expert, and I don't know if the person writing in that thread is either (although their style of writing suggests they might be knowledgeable).

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