As an engineer, I am used to debugging complex systems. Usually, this involves a terminal, some coffee, and tracking down a rogue line of code. But this week, I had to debug my house—and the experience was a literal crawl through the wet soil…

It started with a smell after work.

Not just any smell, but a distinct, noxious, rotting “dead fish” odor emanating from the vicinity of a brick vent on the exterior of our aged house. It was a textbook case: a rat or perhaps a possum had crawled into the subfloor, found a cozy corner, and died. With Sydney’s recent rainy weather, the humidity was practically weaponizing the stench.

I knew what had to be done; otherwise the upcoming summer is going to make it explode. So, I had to go under.

Our house sits on a 3-degree sloped block. The access door is at the lowest point, offering a luxurious amount of headroom (40cm height). But the target vent—the epicenter of the smell—was on the high side of the slope. To get there meant navigating a claustrophobic, ever-narrowing wedge where the wooden floor joists eventually threaten to meet the mud. A true “death triangle.”

I geared up for war, just like the COVID-19 fighters.

I squeezed through the access door and began the commando crawl. It was a wet, miserable journey. I navigated past decades-old electrical wiring pinned to the joists—taking a moment to appreciate that, miraculously, there were zero rat chew marks on them.

Inch by inch, I dragged myself uphill towards the vent. My back was scraping the timber bearers. I was mentally preparing myself for the gruesome sight of a decomposing carcass. I reached the target zone, paused, shone my headlamp into the darkest corners of the cavity, and braced for the smell…

Nothing after 20min inspection all different angles, running out of my phone storage for the video, which was re-inspected multiple times later.

Absolutely nothing. No carcass. No flies. No rotting smell. In fact, there wasn’t even a breeze. The subfloor was completely, utterly empty (except for some aged junks that I don’t bother cleaning them up).

Confused and covered in dirt, I army-crawled all the way back down the slope and squeezed out into the fresh air. I had searched the entire grid. The “corpse” simply did not exist.

Defeated, I walked back inside the house to wash off the grime. And that’s when the plot twist hit me like a ton of bricks.

The smell wasn’t coming from outside. It was inside.

It was by accident that my mom said the Huggies nappy had a weird smell, and I physically smelled it. It was exactly the sight dead fish odor that I was looking for… We recalled it fully, all the odor actually just can from this pack of Huggies nappies we use for our kid.

Yes, just Huggies nappies, after weeks of opening window for fresh airs.

There is a known phenomenon where the super-absorbent polymer (SAP) and adhesives in certain batches of nappies react with high ambient humidity to produce a pungent, chemical “dead fish” smell. And the kicker? We had been enduring this phantom dead animal smell for days, and I had used that cursed pack of Huggies all the way down to the very last nappy.

The vent outside? It was just a coincidence. The nappies were sitting near the interior wall in that exact area, and the smell was playing tricks on my mind.

I had suited up in hazmat gear, crawled through a claustrophobic mud pit, and mentally prepared to hook a dead possum out of a crevice—all for a bag of diapers.

It was absolutely ridiculous. But looking on the bright side? I now know with 100% certainty that my subfloor is structurally sound, the wiring is pristine, and my house is completely rat-free.

Next time I smell something rotting, though, I’m checking the nursery before I put on the knee pads.

Fun living in a standalone house :P