What type of glass must not be used in a window installed less than 18 inches above the floor?

Plate glass should not be used in a window installed less than 18 inches above the floor due to safety concerns. Plate glass is more susceptible to breaking and, when shattered, it tends to break into sharp shards that can cause serious injuries. This is particularly critical in situations where the glass is positioned at a low height, as individuals are more likely to come into contact with it.

In contrast, tempered glass is treated to be much stronger and, when broken, shatters into small, less harmful pieces. Laminated glass, which consists of multiple layers of glass with an interlayer, also provides safety by holding the shattered pieces together. Tinted glass, while it may serve aesthetic or heat-reducing purposes, does not inherently enhance safety in terms of breakage. Therefore, the building codes aim to reduce the risk of injury by prohibiting the use of plate glass in locations where it poses a higher danger.