A hazard is any potential source of harm or adverse health effect on a person or property. Safety professionals classify these sources into several categories, such as chemical, biological, or ergonomic, to better manage risks. Focusing on the physical category helps isolate threats that result from direct environmental or mechanical interaction. This article will explore the nature of physical hazards, providing specific examples that range from structural stability to invisible energy fields.
What Makes a Hazard Physical
A physical hazard is fundamentally an agent, factor, or circumstance that can cause harm without relying on a chemical reaction or a biological process. The resulting injury typically stems from the transfer of energy or direct contact with matter in an extreme state. This transfer can involve kinetic, electrical, thermal, or acoustic energy impacting the body.
The injury mechanism often involves forces exceeding the body’s structural tolerance (crushing or tearing) or energy that damages tissue (burning or overstimulation). These hazards exist as physical entities or states in the environment, ready to cause damage upon exposure. Understanding this distinction is necessary to apply effective preventative measures, which usually involve engineering controls or physical barriers.
Examples Involving Motion and Structure
The most immediate and common examples of physical hazards involve uncontrolled motion or compromised structural integrity in the surrounding environment. Mechanical hazards arise from machinery with moving parts designed to cut, crush, shear, or punch materials. Exposed gears, belts, or rollers create pinch points where two parts move together, posing a risk of entanglement or crushing of limbs.
Unguarded machinery presents a risk where clothing, hair, or hands can be pulled into rotating components, often resulting in severe injuries like lacerations or amputation. Even after a machine is powered off, rotating parts may continue moving due to inertia, necessitating specific safety protocols before maintenance.
Structural and kinetic hazards involve the environment itself and include the risk of falling from heights or injuries from falling objects. A poor housekeeping environment with uneven surfaces, spilled liquids, or obstructions can lead to slips, trips, and falls, which constitute a significant percentage of general injuries. Unsecured loads, unstable scaffolding, or poorly stacked materials create the hazard of falling objects, delivering kinetic energy upon impact. Sharp edges or protruding objects, such as exposed rebar or improperly stored tools, can cause cuts and puncture wounds from direct physical contact.
Examples Involving Environmental Energy
Other physical hazards are less visible and result from the uncontrolled release or presence of environmental energy. Electrical hazards are particularly dangerous because the severity of the injury depends on the current intensity, exposure duration, and the path the current takes through the body. A current as low as 1 milliampere (mA) is the threshold of perception, but 9 to 30 mA can cause muscle contractions so severe that a person cannot let go of the conductor (the “let-go” range).
Currents between 50 and 150 mA can lead to extreme pain, respiratory arrest, and ventricular fibrillation, stopping the heart’s pumping action. Thermal hazards involve extreme temperatures, resulting in tissue damage from the transfer of heat or cold energy. Exposure to high heat, such as from steam or hot surfaces, causes burns, while exposure to intense cold can lead to frostbite and hypothermia.
Noise hazards involve acoustic energy, measured in decibels (dBA), which can damage the sensitive hair cells of the inner ear. Exposure to noise at or above 85 dBA for extended periods (e.g., eight hours) can cause permanent hearing loss. For every 3-dBA increase above 85 dBA, the safe exposure time is cut in half, meaning that 88 dBA is only safe for four hours.
Extremely loud, impulsive sounds, such as a gunshot, can exceed 140 dBA and cause immediate, permanent hearing damage. Radiation hazards involve electromagnetic energy that can be non-ionizing, like intense ultraviolet (UV) light, or ionizing, such as X-rays and gamma rays. Ionizing radiation can penetrate the body and disrupt molecular structures, leading to cellular damage that may result in burns or cancer.