1. What is mg/m³ to PPM Conversion?

Definition: This calculator converts concentration measurements from milligrams per cubic meter (mg/m³) to parts per million (ppm) for gases.

Purpose: It's essential for environmental monitoring, industrial hygiene, and air quality assessments where different units are used.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( PPM \) — Parts per million (volume/volume)
• \( mg/m³ \) — Concentration in milligrams per cubic meter
• \( MW \) — Molecular weight of the gas (grams per mole)
• \( 24.45 \) — Molar volume at 25°C (liters per mole)

Explanation: The formula accounts for the gas's molecular weight and standard temperature conditions to convert mass concentration to volume concentration.

3. Importance of Unit Conversion

Details: Different industries and standards use different units. PPM is commonly used in occupational exposure limits, while mg/m³ is often used in environmental regulations.

4. Using the Calculator

Tips: Enter the concentration in mg/m³ and the molecular weight of the gas. Both values must be > 0. The calculation assumes standard conditions (25°C and 1 atm pressure).

5. Frequently Asked Questions (FAQ)

Q1: Why is 24.45 used in the formula?
A: This is the molar volume (in liters) of an ideal gas at 25°C (298K) and 1 atmosphere pressure.

Q2: How does temperature affect the conversion?
A: The conversion is temperature-dependent. For other temperatures, use: 24.45 × (298/T) where T is temperature in Kelvin.

Q3: Where can I find molecular weights of common gases?
A: Common examples: CO₂ = 44.01, CO = 28.01, O₂ = 32.00, CH₄ = 16.04, SO₂ = 64.06.

Q4: Is this conversion valid for all gases?
A: It works for ideal gases at standard conditions. For high pressures or non-ideal gases, additional corrections may be needed.

Q5: What's the difference between ppmv and ppm?
A: In air quality measurements, ppm typically means ppm by volume (ppmv), which is what this calculator provides.