The basic equipment for bomb technicians includes bomb suits, hazmat protection, and robots. Early bomb suits were nothing more than steel plates carried in a canvas coverall. Today's bomb suits are the result of careful research into the physics of explosions and their physiological effects on humans. Some models provide increased protection against ground reflected pressure waves and 360-degree protection. Many hazmat suits were originally designed for use by personnel responsible for explosive ordnance disposal and unexploded ordnance. The suits are now also used by technicians in chemical, biological, and other hazmat atmospheres. Robots, while expensive, are versatile machines that enhance personnel safety in bomb disposal activities, tactical law enforcement operations, hostage negotiations, and other potentially dangerous activities. Tools such as x-ray equipment and disrupters have seen major improvements, and bomb squads can choose equipment from more diverse options than ever before.