Regarding the conversion between ppm and mg/m3

mg/m3 is the mass-volume concentration, while ppm stands for one part per million and has no units; its unit is ml/m3. The two can be converted to each other using the gas density

In fact, it involves using the ideal gas law to convert the volume concentration into a mass concentration. If it is not at standard conditions, it must be converted to standard conditions in order to use 22.4 in the formula.

PPM stands for one part per million; therefore, all you need to do is ensure that the result you calculate is expressed as one part per million! For example, mg/L is also one part per million

There are many questions on the forum regarding the concentration units ppm and mg/m3; it is recommended that you take a look: Conversion formulas between the concentration units ppm and mg/m3: http://bbs.hcbbs.com/viewthread.php?tid=256205&page=1. Discussions on the measurement units ppm and mg/m3: http://bbs.hcbbs.com/viewthread... ht=ppm%D3%EBmg%2Fm3. What is the relationship between ppm and mg/m3? http://bbs.hcbbs.com/viewthread. ... ht=ppm%D3%EBmg%2Fm3

Anyway, I use LZ’s formula; in the national standard 13223, the conversion factor for NOx is 2.15 and that for SO2 is 2.86 – all values are calculated using this formula

PPM has no units at all; it represents one part in a million

What was said upstairs is correct; it has no units. In English, it’s expressed as parts per million, not using the units used in our country

1.5mg/m3 is approximately 1ppm；

Concentrations related to ppm and unit conversions for concentrations (I): Solution concentration. Solution concentration can be divided into three categories: mass concentration (such as mass percent concentration), volume concentration (such as molar concentration, equivalent concentration), and other types of volume concentration. 1. Mass percent concentration: The concentration of a solution is expressed as the percentage of the mass of the solute relative to the total mass of the solution, and it is denoted by the symbol %. For example, 25% glucose injection means that 100 grams of the injectable solution contains 25 grams of glucose. Mass percent concentration (%) = Mass of solute / Mass of solution × 100%. 2. Volume concentration: (1) Molar concentration – The concentration of a solution is expressed as the number of moles of solute per liter of solution; this is denoted by the symbol mol. For example, if 1 liter of concentrated sulfuric acid contains 18.4 moles of sulfuric acid, then the concentration is 18.4 mol. Molar concentration (mol) = number of moles of solute / volume of solution (liters). (2) Equivalent concentration (N) – this unit is no longer in use; it has been phased out, but it was still frequently mentioned in books from the 1950s. The concentration of a solution, expressed as the number of equivalents of solute per liter of solution, is called equivalent concentration and is denoted by the symbol N. For example, 1 liter of concentrated hydrochloric acid contains 12.0 equivalents of HCl, so its concentration is 12.0 N. Equivalent concentration = number of gram-equivalents of solute / volume of solution (in liters). 3. Mass-volume concentration: The concentration expressed as the mass of solute per unit volume (1 cubic meter or 1 liter) of solution is called mass-volume concentration, and it is denoted by the symbols g/m3 or mg/L. For example, if 1 liter of chromium-containing wastewater contains 2 milligrams of hexavalent chromium, then the concentration of hexavalent chromium is 2 milligrams per liter (mg/L). Mass-volume concentration = mass of the solute (in g or mg) / volume of the solution (in m3 or L). 4. Formulas for converting concentration units: 1) Equivalency concentration = 1000 × d × mass percent concentration / E (where E is the gram equivalent of the solute). 2) Mass percent concentration = equivalency concentration × E / 1000 × d (where d is the density of the solution). 3) Molar concentration = 1000 × d × mass percent concentration / M (where M is the molar mass of the solute). 4) Mass percent concentration = mass-volume concentration (mg/L) / 104 × d. 5) Mass-volume concentration (mg/L) = 104 × mass percent concentration. 5. ppm is often expressed as a percentage by weight; ppm = g/kg = mg/L. That is, 1 ppm = 1000 ug/L. 1 ppb (part per billion) = 1 ug/L = 0.001 mg. 2. For gas concentrations, volume concentration and mass-volume concentration are commonly used to indicate the amount of pollutants in the atmosphere. 1. Volume concentration: Volume concentration is expressed as the volume of pollutants per cubic meter of air, in cm3 or ml/m3. The commonly used unit for expressing this is ppm, where 1 ppm = 1 cm3/m3 = 10-6. In addition to ppm, there are also ppb and ppt. The relationships between them are as follows: 1 ppm = 10-6, which means one part per million; 1 ppb = 10-9, meaning one part per billion; 1 ppt = 10-12, meaning one part per trillion. Additionally, 1 ppm is equal to 103 ppb and 106 ppt. 2. Mass-volume concentration: The concentration expressed as the mass of pollutants per cubic meter of air is called mass-volume concentration, with the unit being mg/m3. The conversion relationship to ppm is: χ = (M / 22.4) × C, which means C = χ × 22.4 / M. Here, χ represents the concentration of the pollutant in mg/m3 ； C—Concentration value of pollutants expressed in ppm ； M—Molecular weight of the pollutant. From the above formula, the following relationship can be obtained: 1 ppm = 22.4 × (mg/m3) / M. Example 1: Determine the ppm concentration of hydrogen fluoride at 30 mg/m3 under standard conditions. Solution: The molecular weight of hydrogen fluoride is 20; therefore, C = 30×22.4/20 = 33.6 ppm. Example 2: Given that the concentration of sulfur dioxide in the atmosphere is 5 ppm, determine its concentration in mg/m3. Solution: The molecular weight of sulfur dioxide is 64. χ = 5×64/22.4 mg/m3 = 14.3 mg/m3