Writing

Notes from the failure side of fire modelling.

Everything here comes out of building and breaking a real CFD pipeline. No thought leadership, no predictions — measured numbers from runs that went wrong, and what it took to make the wrongness visible.

10 August 2026
12 min read
Case study

The run that passed every check and described a bomb

A completed simulation, a successful solver exit, sixteen green checks, and an issued report — for a compartment that reached 0.6 bar. How a smoke model seals itself, why nothing catches it, and the three separate defects we found while fixing the first one.

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10 August 2026
9 min read
Method

We quoted 21.6 hours for a job that was going to take 60

Our compute cost model under-predicted a real run by 2.8×. Not hardware, not mesh count — every calibration point predated the physics we now ship, so the table described a solver doing strictly less work than the one we run. What we measured, what we threw out, and the mistake inside the fix.

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10 August 2026
9 min read
Case study

The report told us it could not check itself, and we filed it as a footnote

Six checks had been quietly not running for months. The system reported it on every affected run, in plain English, and we read it every time — as a warning among warnings. Reporting a problem and communicating one are not the same act.

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10 August 2026
10 min read
Method

Three things make a leak real in FDS, and it warns you about none of them

We declared envelope leakage, the deck contained it, and the pressure trace came back identical to the run with none at all — to five significant figures. What the solver actually requires, why it stays silent, and the two ways a leakage figure goes wrong even when the plumbing is right.

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10 August 2026
10 min read
Method

The upper floors were perfectly tenable, and that was the problem

Every storey above the fire read exactly ambient temperature and full visibility. Not because the smoke control worked — because a horizontal mesh boundary had severed the shaft at slab level. Why horizontal cuts seal and vertical ones do not, and what the signature looks like in someone else’s report.

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10 August 2026
8 min read
Standards

“UK only” is four regulatory regimes, and we were citing the wrong one

Approved Document B has no force in Scotland. Our reference library recorded that correctly and our check register cited it anyway, on every building. The correct fact sat in the codebase the whole time with nothing joining it to the decision that depended on it.

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Why write about our own failures? Because in a liability profession the useful question is never whether a tool works when it works — it is what happens when it does not, and whether anyone finds out. Every piece here exists because something went wrong in a way that was invisible, and the fix is now a check that blocks its own author's work. If that is the sort of thing you would rather know before buying, you are the reader we are writing for.