along the way. It can also be heard from miles away as it has a concussive blast that adds to the effect. Firefighters need to have extreme communication at all times on the fire ground as one broken window at the wrong time could seriously harm anyone operating on the building. Depending on the heat of the fire, burns can occur in a fraction of a second. Additional risks of fire are the obscuring of vision due to smoke, potentially causing a fall or disorientation; becoming trapped in a fire; and structural collapse. "Three hours of fighting a fire stiffens arteries and impairs cardiac function in firefighters" according to a study by Bo Fernhall, a professor in the department of kinesiology and community health in the College of Applied Health Sciences, and Gavin Horn, director of research at the Illinois Fire Service Institute. The conditions (observed in healthy male firefighters) are "also apparent found in weightlifters and endurance athletes..." During debris cleanup Once extinguished, fire debris cleanup poses several safety and health risks for workers. Many hazardous substances are commonly found in fire debris. Silica can be found in concrete, roofing tiles, or it may be a naturally occurring element. Occupational exposures to silica dust can cause silicosis, lung cancer, pulmonary tuberculosis, airway diseases, and some additional non-respiratory diseases. Inhalation of asbestos can result in various diseases including asbestosis, lung cancer, and mesothelioma. Sources of metals exposure include burnt or melted electronics, cars, refrigerators, stoves, etc. Fire debris cleanup workers may be exposed to these metals or their combustion products in the air or on their skin. These metals may include beryllium, cadmium, chromium, cobalt, lead, manganese, nickel, and many more. Polyaromatic hydrocarbons (PAHs), some of which are carcinogenic, come from the incomplete combustion of organic materials and are often found as a result of structural and wildland fires. Safety hazards of fire cleanup include the risk of reignition of smoldering debris, electrocution from downed or exposed electrical lines or in instances where water has come into contact with electrical equipment. Structures that have been burned may be unstable and at risk of sudden collapse. Standard personal protective equipment for fire cleanup include hard hats, goggles or safety glasses, heavy work gloves, earplugs or other hearing protection, steel-toe boots, and fall protection devices. Hazard controls for electrical injury include assuming all power lines are energized until confirmation they are de-energized,