A system of plastic curtains closes the space around a worker in PPE. As soon as person enters the space is filled with cool air and vented to improve heat transfer. The system work due to conductive cooling as well as by radiative cooling from the surroundings.
The head would not be immersed in the cold air, here it is preferable to provide air as clean and virus free as possible.
The heat transfer in the PPE should be improved while being in the cold area. This could be done by using a fan that is switched on when cooling is performed.
Wearing a vest with phase change material would probably be counterproductive, as this vests require a heat insulation to work properly.
The effect will be the best, if the heat balance inside the PPE is not too worse. In that case the cooling time would be limited. If a users works at 34 °C, he will have no heat transfer. So all 300 W have to be removed during the limted time of cooling. So 30 minutes working with 300 W heat production, requires 30 minutes of cooling with 600 W, but 90 minutes of cooling with 400 W.
But if the worker is efficiently resting, he may produce only 100 W internally.This would make the system more efficient: 30 minutes working with 300 W heat production, requires 30 minutes of cooling with 400 W and 90 minutes of cooling with 200 W.
Most of the technique is outside of the infectuous area. The curtains could be operated from outside, so that physical contact between the health care worker and the system is minimized.
The worker should be able to sit somewhere, so that the internal heat production during the cooling phase is minimized.