time-weighted average

time-weighted average

[¦tīm ‚wād·əd ′av·rij]
(science technology)
The average exposure to a contaminant or condition (such as noise) to which workers may be exposed without adverse effect over a period such as in an 8-hour day or 40-hour week. Abbreviated TWA.
References in periodicals archive ?
In most instances, individual states adopted an exposure level of 5,000,000 particles per cubic foot (ppcf) of total dust (not only asbestos fibers) of air based on a time-weighted average over an eight-hour work day.
While the principal measure to assess silica exposure levels and provide a basis for reduction actions has been shift-long time-weighted average (TWA) exposure sampling, measuring real-time exposure enables metalcasters to quantify and prioritize root causes of silica exposure.
Federal law requires employers to protect worker hearing whenever noise exposures are at or above an 8-hour time-weighted average of
Time-weighted average THM concentrations (micrograms per liter) were multiplied by individual water use and THM uptake factors [micrograms/(micrograms per liter)liter for consumption or micrograms/(micrograms per liter) min for showering/bathing] to estimate whole pregnancy and trimester-specific average THM uptake into blood (micrograms/day) for each activity (water consumption, showering, bathing).
The final rule establishes a permissible exposure limit (PEL) for respirable crystalline silica of 50 micrograms as an eighthour time-weighted average that was opposed by industry as unnecessary, not feasible, and not supported by scientific evidence.
The time at temperature histogram can be used to construct a time-weighted average x-factor by simply proportionally weighting the number of hours per year at a given temperature with the associated x-factor for that temperature.
The purpose is to determine if an employee is affected by work-related hearing loss as a result of possible noise exposure in those work environments found to exceed the Action Level threshold of an 8-hour time-weighted average of 85 decibels measured on the A-scale.
Various studies performed over the past years have led to the original 200 part per million (ppm) eight-hour time-weighted average exposure guideline for nPB being gradually downgraded.
In their retrospective analysis of oxygen data collected as part of the routine clinical care of 101 patients mechanically ventilated for [greater than or equal to] 48 hours up to the first seven days of ventilation, they found patients were generally ventilated with settings that achieved liberal oxygenation, typified by their observation that, overall, a time-weighted average fraction of inspired oxygen (Fi[O.
Using a flow-weighted average rate to calculate fan power is not equivalent or even close to the time-weighted average fan power from different operation modes.
Federal guidelines set a maximum occupational exposure limit at 5,000 ppm as a time-weighted average for an eight-hour workday.