**Light coefficient (SK) **is the ratio of the area of the glass surface of windows (without frames and bindings) to the floor area of the room. It is expressed by an ordinary fraction, the numerator of which is the value of the glazed surface in m 2 , and the denominator is the floor area. The numerator of the fraction is reduced to unity; for this, both the numerator and the denominator are divided by the value of the numerator.

*Example.*

*The room has two identical windows, the glazing area of one window is 1.5 m **2 **, the floor area is 24 m **2 **.*

*SK = S windows / S floor = (1.5 • 2) / 24 = 1/8*

If the window has a complex configuration and curly overlap, then to simplify the calculation of SC, it is allowed to reduce the glazing area by 20-25%.

In treatment rooms, dressing rooms, medical rooms, and drawing rooms, the SC should be equal to 1 **: **2-1 **: **5 (exact work); in rooms where medium-precision work is performed – 1 **: **6–1 **: **8; in residential premises – 1 **: **8-1 **: **10; in auxiliary and storage rooms – 1 **: **10–1 **: **14.

SK does not take into account the shading factors inside and outside the room, the configuration and placement of windows, the depth of the room, therefore, an additional study of other geometric indicators is advisable .

**The coefficient of penetration (laying) **is the ratio of the room **depth ( **distance from the window – light-bearing wall) to the opposite wall) to the distance measured from the upper edge of the window to the floor. Good lighting provides a penetration coefficient not exceeding 2.5.

**Angle of incidence**

allows you to judge the amount of light flux illuminating the workplace. He arr azuetsya two lines, one of which, Horizon tal (ac) carried ditsya of determining the place (table surface) to the LO him edge of the window, and the other – from the point of definition to the upper edge of the window (ab). Hygienic standard for angle of incidence (α) – 27o.

**The angle of the hole **takes into account the dimming effect of opposing buildings and allows us to judge the amount of direct and direct sunlight scattered from the sky. It is formed by two lines, of which one (upper – ab) goes from the definition to the upper edge of the window, and the other (lower – ad) goes to the highest point of the opposing building, visible through the window. The minimum allowable angle of the hole (β) is 5o.