Physical Hazards Flashcards

What are the three fundamental principles of radiation protection (for ionising radiation)?

Answer: Time (minimise exposure duration), distance (maximise distance from source), and shielding (use appropriate barriers)

The three principles of radiation protection are: (1) Time — reduce the duration of exposure to reduce the total dose received, (2) Distance — increase the distance from the source (dose decreases with the square of the distance — inverse square law), (3) Shielding — place appropriate materials between the person and the source (lead for gamma/X-rays, perspex for beta, paper for alpha).

What are the health effects of exposure to ultraviolet (UV) radiation in the workplace?

Answer: Sunburn (erythema), skin cancer (melanoma and non-melanoma), premature skin ageing, arc eye (photokeratitis), and cataracts

UV radiation causes acute effects including erythema (sunburn) and arc eye (painful inflammation of the cornea from welding arcs). Chronic effects include skin cancer (both melanoma and non-melanoma types — outdoor workers have increased risk), accelerated skin ageing, and cataracts. UV-C is mostly absorbed by the atmosphere but is produced by germicidal lamps and welding arcs.

What is the 'dead man's handle' or 'hold-to-run' control and on what type of equipment is it commonly used?

Answer: A control device that must be continuously held by the operator for the equipment to operate, automatically stopping if released — commonly used on portable grinders, chainsaws, and mobile plant

A dead man's handle (hold-to-run control) requires continuous deliberate pressure from the operator. If the operator releases the control — due to injury, loss of consciousness, or losing grip — the equipment immediately stops. It is used on portable power tools (angle grinders, chainsaws), mobile plant (some forklift trucks), and railway locomotives. It provides last-resort protection against uncontrolled operation.

What is the purpose of health surveillance for workers exposed to vibration?

Answer: To detect early signs of HAVS or WBV-related conditions before they become disabling, allowing intervention to prevent further damage

Health surveillance for vibration-exposed workers aims to detect early symptoms of HAVS (tingling, numbness, blanching of fingers) or WBV effects (back pain, spinal changes) before they progress to disabling conditions. It typically involves a tiered approach: initial screening questionnaire, followed by clinical assessment by an occupational health professional if symptoms are reported. Results inform control measures and individual exposure decisions.

Under electrical safety principles, what is the purpose of earthing (grounding) metal-cased electrical equipment?

Answer: To provide a low-resistance path for fault current to flow safely to earth, causing the protective device (fuse/MCB) to operate and disconnect the supply before a dangerous touch voltage develops on the metalwork

Earthing connects exposed metalwork of electrical equipment to the general mass of earth via a low-resistance conductor. If a live conductor contacts the metal case (an earth fault), the low-resistance earth path allows a high fault current to flow, which operates the protective device (fuse or MCB) to disconnect the supply rapidly. Without earthing, the metalwork would become live at mains voltage, creating a lethal shock hazard.

What safe operating limits must be established for a pressure system under PSSR 2000?

Answer: Safe operating limits must cover the maximum and minimum permissible pressures, temperatures, and any other parameters that could affect system integrity

PSSR 2000 Regulation 7 requires the user of an installed pressure system (or owner of a mobile system) to ensure that the safe operating limits are established, including: maximum allowable pressure, minimum allowable pressure (for systems operating under vacuum), temperature limits, and any other operating parameters that could affect the safe operation of the system. These limits must not be exceeded during normal operation.