One such in England (an NHS Nightingale Hospital)
With such open space, how do they plan to separate those who might be ill, from those who is ill and in serious condition? They all breath in one area. Even with up-to-date air cleaning system, some bacterias will move freely in the whole are
Viruses are not bacteria
And as I'm inclined to think, they can be killed with ultraviolet and ozone. That's essentially one of the reasons why open places with a lot of sunshine are relatively safe. Regardless, this is a kind of field hospital where everyone is considered infected. They could run tests before admission, and even if some people free of coronavirus get admitted by mistake, this won't make things particularly worse than they would be without these hospitals