[Exposure assessment strategies for determination of compliance with ceiling occupational exposure limits]

The goal of the assessment of exposure to chemicals is to demonstrate the compliance with occupational exposure limit (OEL). There are numerous publications on recommended air sampling strategies for compliance measurements of time weighted average (TWA) concentrations of chemicals but no clear and unambiguous guidelines for measurements and interpretation of ceiling concentrations can be found. Furthermore, definitions and interpretation of ceiling values in different countries may differ considerably. Systems of establishing ceiling limit values, their definitions and interpretation in Germany, the USA (OSHA, ACGIH and NIOSH), the UK and Poland have been reviewed. In most countries of the European Union and in the USA, continuous monitoring using either self contained instruments, multipoint sampling systems or multiplexed sensors is considered as being the most appropriate approach. Based on the literature review the following air sampling strategies have been proposed:--for substances with both OEL--Ceiling and OEL-TWA values dual sampling: 8-hour samples for time weighted average concentrations, and in parallel short (5-10 min) samples during the expected highest exposure for ceiling concentrations measurements; for substances with OEL--Ceiling as the only exposure limit (which is preferable); continuous monitoring using direct reading instruments, possibly with an alarm device. If such instruments are not available, short time measurements may be performed at regular (30 min) intervals using direct reading gas analysers or detector tubes.