A patient enclosure, comprising: at least two spaced-apart side walls (22, 24), a top wall, and a front wall, said side walls (22, 24), said top wall, and said front wall defining a predetermined area surrounding a location where a patient is positionable; an opening through one of said walls (22, 24) allowing access into said area; a door within said opening, said door movable between an open position allowing access to said area and a closed position preventing access to said area; UV radiators within said area of said enclosure; and an air circulation system for circulating air through said area defined by said enclosure, said air circulation system comprised of: a conduit having distal ends communicating with said area within said enclosure at spaced-apart locations in said enclosure; a blower for blowing air through said enclosure; an air filtration system (126, 132, 134, 136) connected to said conduit such that air flowing through said conduit is filtered by said air filtration system (126, 132, 134, 136); an air inlet connecting said area within said enclosure with the environment surrounding said enclosure, said air inlet having an inlet valve controlling air flow therethrough; an air outlet connecting said area within said enclosure with the environment surrounding said enclosure, said air outlet having an outlet valve controlling air flow therethrough; and a controller controlling said UV radiators, said blower, said inlet valve, and said outlet valve, said controller programmed to create one of a higher pressure or a lower pressure within said area as compared to the environment surrounding said enclosure; and wherein said front wall, said side walls (22, 24), and said top wall are dimensioned to be joined with a side wall and a floor of an existing structure to define said enclosed area, wherein said side wall of said existing structure forms a back wall of said enclosure; characterized by at least one of said walls (22, 24, 26, 28) having a panel of electrochromic glass that is switchable between a clear state and an opaque state. at least two spaced-apart side walls (22, 24), a top wall, and a front wall, said side walls (22, 24), said top wall, and said front wall defining a predetermined area surrounding a location where a patient is positionable; an opening through one of said walls (22, 24) allowing access into said area; a door within said opening, said door movable between an open position allowing access to said area and a closed position preventing access to said area; UV radiators within said area of said enclosure; and an air circulation system for circulating air through said area defined by said enclosure, said air circulation system comprised of: a conduit having distal ends communicating with said area within said enclosure at spaced-apart locations in said enclosure; a blower for blowing air through said enclosure; an air filtration system (126, 132, 134, 136) connected to said conduit such that air flowing through said conduit is filtered by said air filtration system (126, 132, 134, 136); an air inlet connecting said area within said enclosure with the environment surrounding said enclosure, said air inlet having an inlet valve controlling air flow therethrough; an air outlet connecting said area within said enclosure with the environment surrounding said enclosure, said air outlet having an outlet valve controlling air flow therethrough; and a controller controlling said UV radiators, said blower, said inlet valve, and said outlet valve, said controller programmed to create one of a higher pressure or a lower pressure within said area as compared to the environment surrounding said enclosure; and wherein a conduit having distal ends communicating with said area within said enclosure at spaced-apart locations in said enclosure; a blower for blowing air through said enclosure; an air filtration system (126, 132, 134, 136) connected to said conduit such that air flowing through said conduit is filtered by said air filtration system (126, 132, 134, 136); an air inlet connecting said area within said enclosure with the environment surrounding said enclosure, said air inlet having an inlet valve controlling air flow therethrough; an air outlet connecting said area within said enclosure with the environment surrounding said enclosure, said air outlet having an outlet valve controlling air flow therethrough; and a controller controlling said UV radiators, said blower, said inlet valve, and said outlet valve, said controller programmed to create one of a higher pressure or a lower pressure within said area as compared to the environment surrounding said enclosure; and wherein said front wall, said side walls (22, 24), and said top wall are dimensioned to be joined with a side wall and a floor of an existing structure to define said enclosed area, wherein said side wall of said existing structure forms a back wall of said enclosure; characterized by at least one of said walls (22, 24, 26, 28) having a panel of electrochromic glass that is switchable between a clear state and an opaque state.