If you can smell your bathroom after someone's been in there — congratulations. You just ate it. Those molecules had to travel from somewhere to reach your nose. They didn't teleport. They hitched a ride on particles. Particles floating through your HVAC right now.
Tell Me How To Stop Eating Poop →When you flush a toilet, it creates an aerosol plume of microscopic fecal particles — some as small as 0.5 microns — that launch into the air and stay suspended for up to 6 hours. Studies from the University of Colorado found these particles travel up to 15 feet from the bowl.
Your HVAC system then helpfully distributes them throughout your entire home. Every room. Every breath. You're welcome.
— Journal of Hospital Infection (2012) · University of Colorado / CU Boulder Aerosol Studies —
Your nose is a particle detection system. It doesn't hallucinate smells — it reports on reality. When your nose says "someone was in that bathroom," what it actually means is: "I just processed airborne fecal matter and you should probably know about it."
// Not all filters are created equal. Most are created useless.
| Filter Type | MERV Rating | Captures Down To | Stops 💩 Particles? |
|---|---|---|---|
| Fiberglass — Builder Grade That flat gray thing you forget exists |
MERV 1–4 | 10+ microns (dust bunnies only) |
Absolutely Not |
| Standard Pleated What most people upgrade to |
MERV 8 | 3–10 microns (pollen, dust mites) |
Barely |
| Pleated MERV 13 ★ Building science sweet spot |
MERV 13 | 0.3–1 microns Captures fecal bioaerosols |
YES 🎉 |
| True HEPA Standalone unit, not your HVAC |
MERV 17+ | 0.1–0.3 microns (viruses, ultrafine) |
YES — but ⚠ |
For your central HVAC system: MERV 13 pleated filter.
It captures particles down to 0.3–1 micron — which covers fecal bioaerosols, bathroom aerosols,
and most airborne pathogens. It does this without strangling your system's airflow
the way a HEPA would. Change it every 60 days (not the 90 on the box — the box lies).
For bathrooms specifically: A standalone HEPA air purifier in or near the
bathroom catches the plume before it enters your ductwork. Run your exhaust fan for
20 minutes post-flush (yes, really — not 2 minutes). This mechanically
removes particles from the air before they get a chance to tour your home.
The combination: MERV 13 in your HVAC + HEPA in the bathroom + 20-min exhaust timer
= you have done what you can for civilization. You're welcome, houseguests.
// If you can smell it, this is what you are breathing
The free guides cover the full indoor air quality picture — filtration, humidity, ventilation, and yes, what's actually floating through your ducts. The AI prompt guide helps you audit your HVAC contractor so they actually fix it right.