Search results
Results From The WOW.Com Content Network
Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m 3, μg/m 3, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude. The change of atmospheric pressure with altitude can be obtained from this equation: [2]
mg/m 3 = milligrams of pollutant per cubic meter of air at sea level atmospheric pressure and T: ppmv = air pollutant concentration, in parts per million by volume T = ambient temperature in K = 273. + °C 0.082057338 = Universal gas constant in L atm mol −1 K −1: M = molecular mass (or molecular weight) of the air pollutant
Its units are in parts per million (ppm) for gases and in milligrams per cubic meter (mg/m 3) for particulates such as dust, smoke and mist. The basic formula for converting between ppm and mg/m 3 for gases is ppm = (mg/m^3) * 24.45 / molecular weight. This formula is not applicable to airborne particles.
Chemical regulation is sometimes [clarification needed] expressed in parts per million (ppm), but often [clarification needed] in milligrams per cubic meter (mg/m 3). [2] Units of measure for physical agents such as noise are specific to the agent.
OSHA Permissible Exposure Limit (PEL): 1 ppm (1.3 mg/m 3) 8-hour Time Weighted Average [43] ACGIH Threshold Limit Value (TLV): 0.01 ppm (0.013 mg/m 3 ) 8-hour Time Weighted Average [ 43 ] The odor threshold for hydrazine is 3.7 ppm, thus if a worker is able to smell an ammonia-like odor then they are likely over the exposure limit.
TSS of a water or wastewater sample is determined by pouring a carefully measured volume of water (typically one litre; but less if the particulate density is high, or as much as two or three litres for very clean water) through a pre-weighed filter of a specified pore size, then weighing the filter again after the drying process that removes all water on the filter.
For chemicals, STEL assessments are usually done for 15 minutes and expressed in parts per million (ppm), or sometimes in milligrams per cubic meter (mg/m 3). [ 4 ] The American Conference of Governmental Industrial Hygienists publishes a more extensive list of STELs as threshold limit values (TLV-STEL).
For carbon monoxide concentrations not exceeding 4 mg/m 3 24-hour mean. [ 2 ] Up to 30 % of Europeans living in cities are exposed to air pollutant levels exceeding EU air quality standards.