MIR VOC Calculations, Values, and Evaporation Rates
Posted on March 1, 2026
Think of MIR as a “smog score” for cleaning liquids. Every solvent has a number that tells us how much it can contribute to forming ozone (smog). To find the MIR of a mixture, we calculate a weighted average of all the ingredients in the blend:
MIR_blend = Σ (m_i × MIR_i)
In simple terms: take each ingredient, multiply it by how much of it is in the blend and its MIR value, then add everything together. The result tells you how “smog-forming” the entire blend is.
Here’s the important update:
Even solvents that are considered “VOC-exempt” under air regulations — like acetone — still have MIR values and must be included in the MIR calculation. They may not count toward VOC content limits, but they absolutely do contribute to ozone formation and therefore must be part of the MIR math.
For example, acetone has an MIR value of 0.36.
Let’s walk through a sample blend:
25% toluene + 25% isopropyl alcohol (IPA) + 50% acetone
Using these MIR values:
- Toluene = 4.00
- IPA = 0.61
- Acetone = 0.36
Step 1 — multiply each ingredient by its MIR:
Toluene: 0.25 × 4.00 = 1.00
IPA: 0.25 × 0.61 = 0.1525
Acetone: 0.50 × 0.36 = 0.18
Step 2 — add them together:
1.00 + 0.1525 + 0.18 = 1.3325
Final MIR of the blend = 1.33 g O₃/g product
Key takeaway:
Even though acetone is VOC-exempt, it still contributes to the overall MIR of the blend. It does not “disappear” from the calculation — it helps determine the total smog-forming potential of the product.
This is why formulators must consider both VOC content and MIR values when designing compliant, low-impact products.
Below are typical evaporation rates expressed as relative evaporation rate (RER) vs. n-butyl acetate = 1.0 at 25 °C.
Notes before you use this in formulations:
- Values vary by data source and test method (ASTM D3539, etc.)
- Temperature, airflow, humidity, and purity affect results
- These are typical industry reference values, suitable for comparative formulation work
Very Fast Evaporating (>3.0)
| Solvent | Relative Evaporation Rate (BuAc = 1.0) | MIR Value (CARB October 2nd, 2010) |
| Acetone (VOC Exempt) | ~5.6 | 0.36 |
| Methyl Ethyl Ketone (MEK) | ~3.8 | 1.48 |
| Methyl Acetate (VOC Exempt) | ~3.1 | 0.07 |
| Tetrahydrofuran (THF) | ~8.0 | 4.31 |
| 1,3-Dioxolane | ~4.0 | 4.96 |
| trans-1,2-Dichloroethene | ~4.5 | 1.7 |
| Cyclohexane | ~6.0 | 1.25 |
| n-Heptane | ~3.3 | 1.02 |
Fast (1.5 – 3.0)
| Solvent | Relative Evaporation Rate | MIR Value (CARB October 2nd, 2010) |
| Ethyl Acetate | ~2.8 | 0.63 |
| Isopropyl Acetate | ~2.3 | 1.07 |
| Methanol | ~3.0 | 0.67 |
| Isopropyl Alcohol (IPA) | ~1.7 | 2.51 |
| n-Propyl Alcohol | ~2.0 | 2.5 |
| Ethylbenzene | ~2.7 | 3.04 |
| m-Xylene | ~0.7 | 9.75 |
| o-Xylene | ~0.6 | 7.64 |
| p-Xylene | ~0.7 | 5.84 |
| 4-Methyl-2-pentanone (MIBK) | ~1.6 | 3.88 |
(Note: Aromatics feel “medium” because although their RER is below 1 in some tables, they evaporate faster than many glycol ethers.)
Medium (0.5 – 1.5)
| Solvent | Relative Evaporation Rate | MIR Value (CARB October 2nd, 2010) |
| n-Butyl Acetate | 1.0 (reference) | 0.83 |
| Cyclohexanone | ~0.3 | 1.35 |
| Isobutyl Alcohol | ~0.9 | 2.51 |
| n-Butyl Alcohol | ~0.3 | 2.88 |
| Secondary Butyl Alcohol | ~1.3 | 1.36 |
| Tertiary Butyl Alcohol | ~2.1 | 0.41 |
| Monochlorobenzene | ~0.4 | 0.32 |
| Dimethyl Carbonate | ~3.2 | 0.06 |
| Ethyl 3-Ethoxypropionate (EEP) | ~0.2 | 3.58 |
| 1-Methoxy-2-propanol (PM) | ~0.3 | 2.44 |
| 1-Methoxy-2-propyl Acetate (PMA) | ~0.4 | 1.7 |
| 2-Methoxyethyl Acetate | ~0.3 | 1.15 |
| 2-Ethoxyethyl Acetate | ~0.2 | 1.84 |
Slow (0.1 – 0.5)
| Solvent | Relative Evaporation Rate | MIR Value (CARB October 2nd, 2010) |
| Isopropyl Acetate | ~2.3 (borderline fast) | 1.07 |
| 2-Butoxyethyl Acetate (EBA) | ~0.1 | 1.62 |
| Dipropylene Glycol Methyl Ether Acetate (DPMA) | ~0.05 | 1.38 |
| Glycol Ether DB Acetate | ~0.04 | 1.38 |
| Propylene Carbonate (VOC Exempt) | ~0.01 | 0.28 |
| Diisobutyl Ketone (DIBK) | ~0.2 | 2.68 |
| Diacetone Alcohol | ~0.1 | 0.6 |
| Benzyl Alcohol | ~0.02 | 5.11 |
| Diethyl Phthalate | ~0.001 | 1.62 |
Very Slow (<0.1)
| Solvent | Relative Evaporation Rate | MIR Value (CARB October 2nd, 2010) |
| Ethylene Glycol | ~0.01 | 3.13 |
| Propylene Glycol | ~0.01 | 2.58 |
| Glycerol | ~0.0001 | 3.15 |
| Diethylene Glycol | ~0.005 | 3.35 |
Glycol Ethers (Typical Values)
| Solvent | Relative Evaporation Rate | MIR Value (CARB October 2nd, 2010) |
| Glycol Ether EB (2-Butoxyethanol) | ~0.08 | 2.9 |
| Glycol Ether PnP (1-Propoxy-2-propanol) | ~0.2 | 2.68 |
| Glycol Ether PnB (Propylene Glycol n-Butyl Ether) | ~0.05 | 2.72 |
| Glycol Ether DPM | ~0.05 | 1.98 |
| Glycol Ether DM | ~0.4 | 2.85 |
| Glycol Ether DB | ~0.02 | 2.39 |
| Glycol Ether DPnB | ~0.03 | |
| Glycol Ether TPM | ~0.01 | 1.92 |
| 2-Ethoxyethanol | ~0.2 | 3.71 |
| 1-Ethoxy-2-propanol | ~0.3 | 3.09 |
| 2-Propoxyethanol | ~0.15 | 3.3 |
Hydrocarbon Solvents
| Solvent | Boiling Range (degrees F) | MIR Value (CARB October 2, 2010) |
| Alkanes (< 2% Aromatics) (Isohexane, Hexane) | 80-205 | 1.42 |
| Alkanes (< 2% Aromatics) (200-230, VM&P, Mineral Spirits, 300-360) | >205-340 | 1.17 |
| Alkanes (< 2% Aromatics) 142 Flash, AGL-LVP | >340-460 | 0.70 |
Practical Formulation Insight (For You)
Since you’re working in:
- VOC/MIR-driven SCAQMD environments
- PCBTF replacement
- Precision cleaning
You typically balance:
- Fast evaporators (acetone, heptane, MEK) → quick flash
- Mid-range carriers (PMA, MIBK, EEP) → solvency balance
- Slow tail solvents (DBE, glycol ethers) → film leveling & soil lift
Excel Document:
• MIR Value VOC Cheat Sheet with Evaporation Rates
Disclaimer
The information presented in this blog reflects the results of our own independent online research. While we strive to provide useful and accurate insights, actual figures, details, and outcomes may vary. We do not guarantee the completeness, reliability, or accuracy of any data referenced. Readers should independently verify all details before making any business, operational, or regulatory decisions.