Barriers are typically designed to defeat defined threats. This is part of building codes as well as fire codes. Apart from external threats, there are internal threats of fire, smoke migration as well as sabotage. The National Building Code of Canada, as an example, indicates the need to defeat external explosions with the building envelope, where they are possible, such as where large electrical transformers are located close to a building. High-voltage transformer fire barriers can be examples of walls designed to simultaneously defeat fire, ballistics and fragmentation as a result of transformer ruptures, as well as incoming small weapons fire. Similarly, buildings may have internal barriers to defeat weapons as well as fire and heat. An example would be a counter at a police station or embassy, where the public may access a room but talk through security glass to employees in behind. If such a barrier aligns with a fire compartment as part of building code compliance, then multiple threats must be defeated simultaneously, which must be considered in the design.