4" Fan - Fur & Chill | HEPA Bed Cooling System

The Overachiever: Fur & Chill 4" Edition

I designed the Fur & Chill 6" Edition first. Then I tested a 4" fan out of curiosity. I didn't expect much. 130 CFM vs 345 CFM is not a fair fight on paper. Turns out fluid dynamics had other plans.

The 4" fan's higher velocity through a smaller duct punches through the HEPA filter more efficiently than the higher volume 6" fan. Pair that with a redesigned oval nozzle and the result is strong, directed airflow in a quieter, more compact, and cheaper package. This is my recommended version for most people.

That said, the 6" isn't obsolete. If you run it on a larger bed, want maximum volume of air moving under the covers, or just sleep like you're trying to recreate a wind tunnel, the 6" still delivers. But for a typical setup where you want effective cooling without waking your partner with fan noise, the 4" is the sweet spot.

The Problem
BUT WAIT — THERE'S MORE AIRFLOW! (Somehow)

Got hot flashes? Partner stealing all the cool air? Just generally melting into your mattress like a forgotten popsicle? I have a solution for you. It only requires a printer, some filament, and the willingness to spend way too many evenings measuring air velocity with an anemometer like a completely normal person.

I stumbled across Paul 2 Travel's brilliant Bed Rocket and immediately thought, "yes, this is exactly what I need." Except I share a house with an 86lb drooling fur monster whose entire life purpose appears to be shedding, and a cat who bullies both of us. Pointing a fan at your bed while living with these two is less "refreshing sleep experience" and more "marinating in a fur tornado all night."

Fur & Chill was inspired by Paul 2 Travel's Bed Rocket, which is still a fantastic solution if you don't need filtration and want something that uses less filament. Go give it a look.

What Fan Do I Need?

Vivosun 4" inline fan: Affordable, widely available, and apparently better at this than it has any right to be.

Tested filter: Levoit Core 300 replacement filter, widely available, affordable, with multiple compatible third-party options if you want to save a few dollars.

A Note on Filters

Not all HEPA filters are created equal for this application. I tested a Shop-Vac HEPA filter and it decimated airflow. Shop-Vac filters are optimized for suction, not continuous airflow from an inline fan. Expect 85%+ airflow loss. Hard pass.

Stick to a dedicated air purifier HEPA filter. These are designed for consistent airflow resistance and work significantly better with inline fans.

I also tested the Levoit Core Mini filter hoping for a more compact option. It reduced airflow to a very gentle breeze. If there's demand I'm happy to upload an adapter for it, but expect lighter airflow.

Assembly Instructions

Step 1 — Filter & Canister
Drop the HEPA filter into the canister. Attach the adapter to the top of the canister (it's a tight fit, expect to “pop” it in)

Step 2 — Fan
Slide the collar/skirt onto the fan, then press the fan into the adapter until seated. There are markings on the fan to tell you which direction air flows.

Step 3 — Ductwork
Connect the long cylinder to the top of the fan. If additional height is needed, attach the optional height extender first (not pictured). Connect the first 45° elbow to the cylinder, then attach the second 45° elbow to the first.

Step 4 — Nozzle & Base
Attach the nozzle to the final elbow. Set the completed assembly into the leg ring base and orient the nozzle toward the head of the bed.