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One part per hundred thousand, per cent mille (pcm) or milli-percent denotes one part per 100,000 (10 5) parts, and a value of 10 −5. It is commonly used in epidemiology for mortality, crime and disease prevalence rates, and nuclear reactor engineering as a unit of reactivity.
The mean time between failures (MTBF, /) is often reported instead of the failure rate, as numbers such as "2,000 hours" are more intuitive than numbers such as "0.0005 per hour". However, this is only valid if the failure rate λ ( t ) {\displaystyle \lambda (t)} is actually constant over time, such as within the flat region of the bathtub curve.
Major dictionaries do not agree on the spelling, [1] [2] [3] giving other options of per mil, [2] per mill, [1] [3] permil, [1] [4] permill, [1] permille. [ 5 ] [ 6 ] The word promille is the cognate in Dutch, German, Finnish and Swedish, and is sometimes seen as a loanword in English with the same meaning as per mille .
The sample also had 4.5 parts per trillion of PFOA, 0.5 above the enforceable limit, and detectable levels of another PFAS, PFHxS, at 5.1 parts per trillion, though that is about half of the limit ...
The examples don't seem to be too accurate. A drop is usually defined as 0.05 ml, which then gives;. 1 drop in 50 ml = 1‰, 50ml is a very small cup 1 drop in 50 l = 1ppm 50 l is about 11 gallons, not 40 1 drop in 50 cubic metres = 1 ppb 1 drop = 1ppt, a 50 m swimming pool is 50*25*2 = 2,500 m^3 1 drop in 50,000,000 cubic metres = 1ppq, 50,000,000 m^3 is equivalent to a lake covering a square ...
1 volume percent = 10,000 ppmv (i.e., parts per million by volume) with a million being defined as 10 6. Care must be taken with the concentrations expressed as ppbv to differentiate between the British billion which is 10 12 and the USA billion which is 10 9 (also referred to as the long scale and short scale billion, respectively).
More recent testing in 2023 by the Georgetown Municipal Water and Sewer Service (GMWSS) detected three PFAS chemicals, but all were below 4 parts per trillion, said Chase Azevedo, general manager ...
It is expressed in terms of nano-grams (ng), pico-grams (pg) or femto-grams (fg) with fg being better than pg better than ng. It can also be expressed in terms of parts per billion (ppb), parts per trillion (ppt) or parts per quadrillion (ppq). Sensitivity is important because most explosives have a low vapor pressure .