Dr Kuo, in surgery with bunnyPAPR
BunnyPAPR in use (1 of 4)
BunnyPAPR in use (2 of 4)
BunnyPAPR, cost comparison
BunnyPAPR, $30, Hospital-grade protection
Dr Kuo, explaining bunnyPAPR, still shot
Safety Testing and Medical Technology Paper (March 2020) BunnyPAPR
Affordable and Scale Fast - Parts List - BunnyPAPR
Air flow diagram with filters, BunnyPAPR
BunnyPAPR in use (3 of 4)
BunnyPAPR in use (4 of 4)
End Screen with tagline, BunnyPAPR
Watch the 5 minute video for an overview.
In March 2020, a short three months ago, Dr Kuo released his design for the Bunny Science PAPR. It was meant to address the N95 shortage in hospitals, but hospital adoption was slow. We asked: For emergency situations, could a $2000 PAPR system be simplified to 1/10th the cost? The answer is yes, and the $30 bunnyPAPR was born.
What it does
The diagram below shows how it works. And one of the key things is that it can be made for $30 or less.
- Contaminated air passes through the FDA-approved anesthesiology viral filter with sub-micron level capture.
- Fan pulls in outside air. Circulates clean air. Provides positive air pressure.
- Person exhales CO2 through a recommended surgical mask. 
- CO2 is continuously vented out rear flutters valves or additional viral filters.
- Fan is powered by USB battery pack in the user's pocket.
Depending on the use case, many of these parts can be decontaminated and re-used. Hence, the one-time cost of $30 is for a reusable system. 
The Bunny Science PAPR has been tested by the inventor, Dr Kuo, an anesthesiologist from Seattle. In particular, it
- passes the nebulized saccharin test (sometimes referred to as the QLFT for respirators)
- passes monitoring of O2 and inspired/expired CO2
- passes "stress tests" of deep and fast inhales and exhales.
It has been worn for 11hours straight. Dr Kuo has also worn it everyday he is in the hospital for the last 2 months.
Details of the Bunny Science PAPR are in the 14-page paper titled: Pilot Evaluation of Oxygen and CO2 Safety of BunnyPAPR, A Prototypical Sealed, Compliant Volume Powered Air Purifying Respirator (SCV-PAPR)
How we built it
About 1000 engineering hours are in on the project.
Four out of five parts are commodity parts. We tested several dozen fans, filters, bags, and batteries to find the right balance.
Commodity Parts List (millions available)
- Fan ($2 wholesale to $4-5 retail)
- FDA-Approved Viral Filters ($1 retail in packs of 100qty)
- Bags ($0.30 each, disposable)
- USB Battery Pack ($5-$10)
The final parts are a head mounting system and airflow-connectors. These were prototyped using 3D-printing. See https://www.bunnypapr.org/makers/3d-print-files
Challenges we ran into
The primary challenge was figuring out our target market. Initially, the focus was on the medical community and at-risk people. After all, they need protection as good or better than N95. However, given the Covid19 controversies around mask wearing mandates, hospital approvals, and cloth masks, we had to admit our error: Not everyone who medically needs one will get one.
The hackathon overcame this challenge by rethinking the problem. "Who is most motivated (financially, medically, or behaviorally) to want bunnyPAPR?" We refocused on international aid (free distribution) and large industries (premium) where safety is part of the license to operate. Hence, we figured out the need for a "Freemium" business model described in the 5-minute video.
Other challenges included various R&D and scaling/sourcing challenges.
- FANS We bought over a dozen fans, many did not match the listed specs.
- BAGS We have spent approximately 125-200 hours on bags. Some bags are strong, but visibility is poor. Other bags have great visibility, but might tear easily.
- INDIA Our India partner (link has had a hard time sourcing the right bags and fans.)
Overall, we are approaching these issues methodically and finding adequate solutions. Importantly, we've been able to maintain our $30 target.
Accomplishments that we're proud of
- All volunteer team. We run through a Discord/Slack chat server.
- Doing all this fast! (2 months, with a flurry in the last 3 weeks).
- Integrating a diverse group of talented volunteers. From 16yo to 70+. Finding good, helpful people internationally.
- Distributing 20+ BunnyPAPR's to people who have wanted to use them.
- We have a list of over 30 requests that we are in the process of fulfilling.
What's next for BunnyPAPR
- Finish "500plan" bunnyPAPR inventory. Make and distribute 500 internationally.
- More user feedback, refine target market.
- Seek "angel" investors for scaling to 2000-5000 and then 100,000
- Explore target markets, like
- NBA and other large markets,
- direct to consumer, and
- WHO, and international humanitarian aid (thanks to help of UCSF Hackathon Mentors)
- Consider US medical markets and FDA Emergency Use Authorization (EUA) approval. Medical regulations are very complex.
- Provisional patent submission
 NOTE on surgical masks. In the "consumer" version, bunnyPAPR™ has viral filters on the intake and exhaust. Hence, surgical masks are not necessary. In one lower-cost "medical" version, bunnyPAPR™, has a viral filter on the intake only and a valve on the exhaust to prevent reverse flow. A surgical mask will capture any viral shedding from the wearer instead of an exhaust filter. This option is because many hospitals administrators will still require a surgical mask or N95. The reason is for legal/FDA-compliance reasons. The decision of which version to use will ultimately be up to the hospital administrator and infectious disease control department.
 The decision on re-use and decontamination is a tricky one. Under normal circumstances of abundant filters, the viral filter would be replaced after each use, just like N95s. Under the Covid19 crisis, many hospitals are rationing and re-using N95 masks, sometimes using one-per-day or even one-per-week. If this is worn in a consumer setting (grocery shopping, not a hotspot), a set of 3 filters would probably last months to a year, depending on how often one goes out. If this is worn in a hospital setting in a Covid19 ward, it will depend on the availability of viral filters. One filter per day or several days is reasonable and similar to the N95 rationing protocols. A lot will depend on the infectious disease control departments in hospitals and national/international health authority guidance. Note: The bunnyPAPR system is not yet FDA-approved, but the viral filters are FDA-approved and routinely used during surgery.