Air filtering unit & positive pressure suit (COVID-19)

Air filtering unit & pressure suit (COVID-19) - Front view 2
Front view 2

Intro:

In 2020 due to COVID-19 pandemic the whole world has got crazy. Airplanes stopped flying, many countries declared state of emergency, many hospitals are full of infected people and much more stuff like that. This sounds insane, doesn’t it ?
Nevertheless, we have to deal with this global crisis somehow…
Makers all around the world are trying to help hospitals and other people in need by designing and manufacturing some useful stuff like respirator parts , masks, face shields etc.

The idea for this project came to my mind when I saw positive pressure suits in the “Contagion” film. They are using these in labs where they handle dangerous viruses and other nasty stuff. The main problem with this suit is that it must be connected to a hose supplying filtered and compressed air which is not available outside the lab of course.

To solve this problem I’ve designed a AFU (Air Filtering Unit) which is responsible for filtering , purifying the air and pumping it into the suit. Because of the positive pressure inside ,the suit doesn’t need to be 100% air tight. Why is that? Well, the answer is quite simple – contaminated air around you will be repelled by air that is coming out from the suit. Because of that you will always breathe with a clean filtered air (assuming that filters capture every dangerous particle).

With such a suit, entering the contaminated zone should be relatively safe.

Air filtering unit & pressure suit (COVID-19) - Honeywell BSL4 positive pressure suit
Honeywell BSL4 positive pressure suit

DISCLAIMER
I am not able to test this device in a scientific way. If you print and wear one of these in a hazardous situation you will be doing it at your own risk!

 

Air filtering unit renders:

Air filtering unit & pressure suit (COVID-19) - Exploded-view render
Exploded-view render

In the render above you can see how the whole thing goes together. 3D model does not include small items like screws nuts and washers. Everything was designed in the way that it can be easily printed on most of the FDM printers (adjusted clearances etc.).

Most of the parts were printed from PETG, ABS and PLA filament.

If you want to redesign some parts or adjust the whole thing to your needs, you can download all CAD files from the link at the bottom of this page.

Air filtering unit & pressure suit (COVID-19) - Front view render
Front view render
Air filtering unit & pressure suit (COVID-19) - Top view render
Top view render
Air filtering unit & pressure suit (COVID-19) - Bottom view render
Bottom view render

Filter chamber:

Air filtering unit & pressure suit (COVID-19) - Filters chamber - disassembled 2
Filters chamber – disassembled 2

The whole thing was designed in the way that filters can be easily swapped. In this prototype I’ve used 3 layers of filters:  fabric filter from medical mask, HEPA filter and activated carbon air filter. Because of modular design more layers of filtering stuff can be easily added. So wheres the catch? Well, you can’t add too many filters that restrict air flow too much – the turbine might not have enough power to push air through them to provide sufficient air flow.

You can choose whatever filters you want, the filters that I’ve used are only one of many possible solutions.

Down below You can find some photos of each filtering stage as well as short description.

3 rd stage – activated carbon filters

3 rd stage is made from 3 layers of activated carbon cloth. The purpose of this stage is to catch and absorb everything that might have passed through the first two filters. A fancy honeycomb mesh prevents carbon cloth from being sucked into the turbine. All filters above this stage and below second stage are supported by this structure.
I have also an idea to fill honeycomb mesh with activated carbon particles from water filter to add even more layers of filters.

If you want too add more fancy types of filters you can stack them above this stage and below second stage HEPA filter.

Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 3
Filter chamber – disassembled 3
Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 6
Filter chamber – disassembled 6
Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 5
Filter chamber – disassembled 5

2 nd stage – HEPA filter

You can easily find thousands of HEPA filters in different shapes that are intended for use in vacuum cleaners or air purifiers. The filter that I’ve bought was intended for use in vacuum cleaners. This particular filter restricts air flow quite much but I hope that it is able to filter out most of the nasty stuff. It is sealed with a gasket which was included with the filter.

Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 7
Filter chamber – disassembled 7
Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 8
Filter chamber – disassembled 8

1 st stage – medical mask filtering material

This stage is intended to catch most of the bigger particles. It should be replaced or washed quite often to make sure that nasty particles which contain viruses don’t contaminate and “clog” rest of the filters. It is also supported by a thin honecomb mesh.

Air filtering unit & pressure suit (COVID-19) - Front view 1
Front view 1
Air filtering unit & pressure suit (COVID-19) - Filters chamber - disassembled 10
Filters chamber – disassembled 10
Air filtering unit & pressure suit (COVID-19) - Filter chamber - disassembled 9
Filter chamber – disassembled 9

Turbine:

I’ve used a turbine extracted from HP BLc7000 server fan unit. To be honest , I was surprised how powerful this small turbine is. I think that it is at least as powerful as leaf blower. When it is turned on at full power it is very noisy, it sounds like a mini jet engine. This particular turbine uses a BLDC motor, therefore it needs a driver to function properly. Fortunately, driver PCB that was inside HP BLc7000 fan unit can be easily hacked and reused. I’ve been trying to implement a smooth adjustment of speed, but I haven’t found any simple solution, deeper reverse engineering is required. As it turned out later there actually is a pin responsible for speed control, unfortunately it allows you to set between 2 speeds only (mid and max RPM). I’ve soldered a switch to this pin.

Air filtering unit & pressure suit (COVID-19) - HP BLc7000 Fan
HP BLc7000 Fan

The whole turbine is very well made, it was cast from magnesium alloy. At this price (I’ve paid about 5$/piece at local store) it is a total bargain !

The turbine on max RPM draws approx. 50 – 70 W.  I think it is possible to get more “juice” from it by using external ESC.

Down below I’ve attached quite good video which shows how the whole thing works:

Pressure suit & tests:

Air filtering unit & pressure suit (COVID-19) - Pressure suit test 3
Pressure suit test 3
Air filtering unit & pressure suit (COVID-19) - Pressure suit test 2
Pressure suit test 2
Air filtering unit & pressure suit (COVID-19) - Pressure suit test 1
Pressure suit test 1

The whole pressure suit will be made from thick trash bags, everything will be cut to size and glued together with adhesive tape. As I mentioned before, it doesn’t have to be 100% leak-proof. For now I’ve made only a helmet with a viewfinder to protect my head which is the most vulnerable part of our body. Fresh air is being pumped by AFU through hose. Air that I breath out is being pushed out through gap around my neck.

Air filtering unit & pressure suit (COVID-19) - Pressure suit test 5
Pressure suit test 5

More photos:

Air filtering unit & pressure suit (COVID-19) - Motor driver PCB 1
Motor driver PCB 1
Air filtering unit & pressure suit (COVID-19) - Rear view
Rear view
Air filtering unit & pressure suit (COVID-19) - Switches
Switches
Air filtering unit & pressure suit (COVID-19) - Motor driver PCB 2
Motor driver PCB 2
Air filtering unit & pressure suit (COVID-19) - Pressure suit test 6
Pressure suit test 6
Air filtering unit & pressure suit (COVID-19) - Bottom view
Bottom view

Other possible uses of AFU:

  • Turbo – soldering fume extractor

I’ve tested it and it can filter out soldering fumes from about 0.5 – 1 m away – that’s insane !

  • Dremel dust extractor

It may find use in filtering out dust which comes from grinding, so that you don’t have to wear a face mask.

Links:

Summary:

I hope that I’ve inspired you to create similar devices which may contribute to stopping spread of COVID-19 virus.

Stay at home, follow the quarantine rules and everything will be fine, we will go through it! 

 

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