Bear Glass Transparent Wall Units make up the final category of fire-rated glass, and in reality, they are in a class by themselves. They are tested and classified as "walls," even though they are made of glass. Their claim to fame is their resistance to heat tranfer. Transparent wall units can actually block significant amounts of heat from transfering through the glass. A fire could be raging on one side and you could literally still place your hand on the other side of the glass. For areas such as stairwells where people could be trapped for long periods of time, or in sensitive computer areas, or where large expanses of glass are used, transparent wall panels serve a genuine need.
There are different kinds of these products on the market. Some are insulated units filled with a clear gel that turns to an opaque foam during a fire. Others are made of multiple layers of glass (similar to bullet resistant glass) with intumescent interlayers that turn opaque during a fire. Both styles of products have ratings of up to 2 hours, withstand the fire hose stream test and offer high impact safety ratings. Thanks to new framing that is now available, architects can incorporate these transparent wall and door units from floor to ceiling in their designs, and still offer 2 hour fire protection.