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Active or Passive Cooling Built into PPE Clothing or Worn Underneath

The relief of stress and discomfort of wearing PPE in hot and humid conditions could be provided by either an active or passive cooling mechanism worn underneath or built into the PPE equipment. One simple passive cooling mechanism that could provide airflow essentially for free would be a chimney. A chimney in PPE would be tubing that routes through the back of the PPE suite which has filtered cold air intake and hot air exhaust near the shoulder area. As the body heats up inside the PPE, the air in the chimney (tubing) will get warmer and naturally rise upward drawing in cooler outside air and exhausting warm humid air.

Photo of jlocke8 .

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Chimney effect cooler built into PPE:
One idea for a cheap and energy free solution for providing passive cooling to the care worker wearing PPE, the PPE could be modified to include tubular structures mounted to the back of PPE suit which have N99 filters on each side of the tube.  The input tube will route near the back around the buttocks and the exit port would be by the back of the head.  Due to the chimney effect as the body heats the air within the chimney tubes, the hot air will rise out and cold air near the bottom of the body will take its place.  This effect will be minor but may be sufficient to drive enough airflow for the careworker to keep dry and cool.  The tubular structures would be wide enough to allow sufficient space for the air to flow and be ridged enough such that the chimney is not kinked or obstructed when the careworker bends or turns.

The chimney tubes could either be completely isolated from the body and mounted to the outside of PPE and have metal panels that conduct heat away from the body similar to a air-to-air heat exchanger (like wearing a backpack of metal tubes), OR the chimney tubes could have filters on each end to filter the air into the suit and then back out, the filters would restrict airflow but would allow humid air to escape.

A small and unexhaustive list of cooling technologies that can be worn:

Active cooling:
-Fluid that is chilled by an A/C that is pumped throughout tubing embedded into the clothing.  
-Peltier device that contacts skin directly

Passive cooling:
-Ice packs / gel-packs that are pre-cooled in a freezer to be worn underneath or into PPE
-Phase change material that is solid but absorbs heat from user and turns liquid
-Evaporative cooling. (what if the PPE itself could sweat and cool off?)
-Heat pipes

Several products already exist that incorporate some of these technologies:

These technologies could be built into PPE such as having a cooled liquid routed through its fabric or inside pockets that can store pre cooled ice-packs.

One of my thoughts to incorporate a passive cooling technique into the PPE suit would include having a thermal conductive panel (such as an aluminum metal panel or thermal interface foam)  in intimate contact with one of the warmest parts of the body (IE either the neck, the back/chest, armpits, or crotch) that is also able to conduct heat outside of the PPE.  Think of it like a computer processor heatsink for the body.  The thermal panels of the PPE would still maintain a water tight barrier from viruses but provide a thermal pathway for the heat to escape to the outside.  To amplify the cooling effect through the thermal panels, one could actively cool this panel from the outside such as using evaporative cooling method and forced airflow or attaching a Peltier device to the thermal panel.


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Photo of Shannon

I think your idea about wearing the cooling device under the PPE is key... by being worn underneath it will not be contaminated, and if it is a separate component from the PPE perhaps it can be re-worn and re-used (rather than being thrown out after each use) in order to keep cost down.

Also, am I understanding this correctly that the current PPE is essentially like wearing a plastic bag? It seems to me that keeping the temperature down and removing moisture would both be important. Your idea in conjunction with the desiccant idea might work well.

Photo of jlocke8

Thanks for the input! I hadn't thought to combine the two. Yea I think PPE is basically like putting yourself in a sealed garbage bag or a space suit since it is nearly air tight

Photo of Rainer

Hi Shannon,

a PPE is a plastic bag where sweating becomes impossible. So all cooling has to be done by radiation or convection. Typically it is worn in a style that thick air layers exists, these cause a substantial heat insulation. But worn directly on the bare skin with no air gap and no clothing, thermal conductance is not bad. In that case about 1 °C is the temperature difference on both side.

But in a room with 34 °C ambient temperature the effect is threatening. All heat the body produces is trapped inside the body and start to heat it up.

With kind regards,

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