No Blower Fit My Wife's Mattress Topper, So I Built One

My wife's airflow mattress topper needed a blower to push air through its channels and remove moisture from her skin. But no commercial blower fit what I had built. So I designed and built one from scratch - from fan selection and noise engineering to industrial design and vacuum-cast housing. This is the story of how a custom blower went from concept to a device that now travels to every hospital stay.

If you have not read about the mattress topper itself, start with the previous post about why and how I built it. For the full backstory of my wife's diagnosis, see Part 1, Part 2, and Part 3 of The Engineer Caregiver series.

In the previous post, I described the airflow mattress topper I built for my wife. The topper creates air channels beneath her body to remove moisture from her skin. But the topper alone is only half the system. Without a blower to push air through those channels, it is just a piece of foam and fabric.

I could not find a commercial blower that was compatible with what I had built. So I designed and built one from scratch.

Why Couldn't I Use a Commercial Blower?

When I started this project, there was almost no reference material for building a blower specifically for a patient mattress topper. The closest commercial product I could find was the BedJet 3 Mini, so I used its published specifications as a starting point.

The BedJet 3 Mini specs: temperature range of approximately 19 to 40 degrees Celsius, noise level of 30 to 46 dB(A), power consumption of 50 to 1,500W, unit size of roughly 394 x 267 x 146mm, with an estimated airflow of 40 CFM and estimated static pressure of about 15 mmH2O.

My topper covers less than half the area of a BedJet Cloud Sheet, so it needs less than half the airflow. However, the air must be pushed through a narrow 5cm space filled with POE blocks, which requires higher static pressure. It also needs to travel through a collapsible tube roughly 70mm in diameter and 2 meters long to reach the topper, demanding even more pressure.

Based on this analysis, I set the following requirements for my blower: air temperature from room temperature to 50 degrees Celsius, noise below 30 dB, size no larger than 300 x 200 x 150mm, airflow of 15 CFM, static pressure of 30 mmH2O or higher, and power consumption between 30 and 700W.

The high static pressure requirement ruled out axial fans immediately. I needed a centrifugal fan.

How Do You Find a Quiet Centrifugal Fan for Medical Use?

While no complete blower product existed for my purpose, I was able to find promising centrifugal fan candidates as individual components.

The challenge was meeting both the airflow and noise requirements simultaneously. Most 15 CFM class blowers operate at 38 to 51 dB, well above my 30 dB target. For example, the Delta BFB0712H-F00 delivers 15.33 CFM at 24.8 mmH2O static pressure but produces 38 dB. The Delta BFB0712HH-AWPH has the same airflow and pressure but runs at 51 dB.

The practical solution became clear: use a larger capacity fan and run it at reduced speed to achieve 15 CFM at below 30 dB. A bigger fan turning slower produces the same airflow with significantly less noise.

But a centrifugal fan is only one component. A complete blower system requires an air heater, airflow and temperature control sensors and circuits, a user interface with volume controls, buttons, switches, and a status display panel, an air outlet and inlet, an intake filter, internal structural components to hold everything in place, a housing, a housing support structure, and flip-out hanging hooks mounted on the housing body. All of these had to be designed, sourced, and assembled.

First Test Prototype

I commissioned a specialist to build a first prototype quickly, focusing only on minimum functionality. Appearance was not a priority at this stage, so the housing was 3D printed.

First prototype built for functional testing. Housing was 3D printed.

The prototype was assembled and tested in actual use conditions with my wife's mattress topper.

Finding the right location and mounting method for the outlet air temperature sensor involved considerable trial and error. Different areas near the blower outlet showed different temperatures, so I needed a position that measured a representative air temperature while remaining stable in terms of heat resistance.

I also developed and tested several heater overheat prevention measures for reliability. The control circuit firmware went through multiple revisions.

Despite all this work, the noise was higher than expected.

How Did I Solve the Noise Problem?

I suspected that the internal structure of the housing was significantly contributing to the noise. The possibilities were numerous: intake noise, exhaust noise, housing resonance, and more.

I consulted acoustics experts multiple times. I installed sound-absorbing materials inside the housing. I even attempted to create an anechoic chamber-like space within the unit to reduce noise.

After all these attempts, the conclusion was simple: the most effective way to reduce noise is to use a larger fan and run it at a lower speed. Everything else was secondary.

Making the blower bigger was the most efficient path to making it quieter.

Second Prototype

My wife is frequently hospitalized, and the blower goes with her every time. Appearance matters when your equipment sits in a hospital ward where nurses, doctors, and other patients see it daily.

I engaged a professional design firm. I explained the mattress topper system, provided sketches of the blower concept, and waited several weeks for design proposals.

Concept sketch provided to the design firm.

Design proposals from the firm.

When the designs came back, I held a review meeting with the relevant specialists and selected the final model.

Design review meeting with specialists.

Based on the selected design, I commissioned the blower fabrication. With the larger housing came a new centrifugal fan, heater, sensors, and circuit components. The control module was rebuilt from the ground up. The housing was manufactured using vacuum casting.

Blower components and connectors before assembly.

Blower before final assembly.

Completed blower unit.

Blower connected to the airflow mattress topper, completing the system.

What Did Building This Blower Teach Me?

Building this blower reinforced something I have learned many times throughout my engineering career: theoretical thinking is important, but building and testing is the fastest path to answers. You can analyze noise sources on paper for weeks, but running the prototype for five minutes tells you more.

I also learned that safety must be designed in from the start, not added later. The blower contains a heater, and overheat prevention is not optional. The protection measures need to be reliable and redundant, and they need to be considered at the earliest design stage.

Most importantly, I confirmed that making the blower larger was the single most effective way to reduce noise. A bigger fan running at lower speed delivers the same airflow with dramatically less sound. When space and weight allow it, bigger is quieter.

The airflow mattress topper system is now complete: the topper, the blower, and the connecting tube. My wife uses it every day. Our caregiver Ms. Kim packs it for every hospital visit. It has become as essential as the ventilator or the suction machine.

It started with a problem no commercial product could solve. It ended with a system built by an engineer for the person he loves most.

Kwonhee Kim

Written by: Kwonhee Kim, engineer, professor, and full-time caregiver to his wife living with Parkinson's disease dementia since 2006. He writes about the intersection of engineering and caregiving at The Engineer Caregiver.

This post reflects personal experience only and is not medical advice. See our Disclaimer.

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Read More from The Engineer Caregiver

• Part 1: Early-Onset Parkinson's Dementia at 47 - The Signs I Missed
• Part 2: After the Diagnosis - How an Engineer Became a Caregiver
• Home ICU for Parkinson's Dementia: How an Engineer Built a Hospital in His Living Room (Part 3 of 3)
• The Airflow Mattress Topper I Built for My Wife: Why and How | DIY Bedridden Care

Frequently Asked Questions

Why can't you use a commercial blower like BedJet for a patient mattress topper?

Commercial products like the BedJet 3 Mini are designed for comfort, not medical caregiving. A custom patient mattress topper requires higher static pressure (30 mmH2O vs. 15 mmH2O) because air must pass through a narrow 5cm space filled with POE blocks and travel through a 2-meter collapsible tube. No off-the-shelf unit met these combined requirements.

How do you reduce noise in a centrifugal blower below 30 dB?

The most effective method is to use a larger capacity fan and run it at reduced speed. A bigger fan turning slower produces the same airflow with significantly less noise. Sound-absorbing materials and housing design provide secondary benefits, but fan sizing is the primary factor.

What materials were used for the blower housing?

The first prototype used a 3D-printed housing for rapid iteration. The second prototype housing was manufactured using vacuum casting, which produces a smoother, more durable finish suitable for daily hospital use.