LPG vs Compressed Gas Aerosols: How to Choose the Right Propellant
The propellant you choose affects everything: equipment configuration, facility safety requirements, product performance, and cost per can. This guide compares liquefied gas propellants (LPG, DME) with compressed gas propellants (N₂, CO₂, compressed air) to help you make the right decision for your product.
The Fundamental Difference
| Characteristic | Liquefied Gas (LPG, DME) | Compressed Gas (N₂, CO₂, Air) |
|---|---|---|
| State in Can | Liquid + vapor — maintains constant pressure as long as liquid remains | Gas only — pressure drops as product is used |
| Pressure Curve | Flat — consistent spray from first to last use | Declining — spray weakens as can empties |
| Spray Characteristics | Fine mist, good particle size control | Wetter spray, larger particles |
| Solubility | LPG: oil-soluble only. DME: water-soluble. | Neither dissolves in product (separate phase) |
| Flammability | Yes — explosion-proof equipment required | No — standard equipment acceptable |
| Equipment Cost | Higher — explosion-proof rated + booster pump | Lower — standard gas filling setup |
| Propellant Cost per Can | ~$0.02-0.04 | ~$0.005-0.01 |
LPG (Liquefied Petroleum Gas)
LPG — a mixture of butane and propane — is the most widely used aerosol propellant globally. It accounts for approximately 70% of all aerosol products.
Advantages
- Constant pressure: As long as liquid LPG remains in the can, the vapor pressure stays stable — typically 3-5 bar at room temperature. This produces consistent spray quality from the first spray to the last.
- Low cost: LPG is a byproduct of petroleum refining and natural gas processing. It is the cheapest propellant option on a per-can basis among liquefied gases.
- Fine atomization: LPG produces small, uniform droplets — ideal for air fresheners, insecticides, and any product where spray pattern quality matters.
- Mature supply chain: Available worldwide with established safety standards, storage infrastructure, and handling procedures.
Disadvantages
- Flammable: LPG-air mixtures are explosive in concentrations of 1.8-9.5%. Production facilities require explosion-proof electrical classification, gas detection systems, and separate propellant storage.
- VOC regulations: LPG is classified as a Volatile Organic Compound. California CARB and EU regulations increasingly restrict LPG use in consumer products.
- Oil-soluble only: LPG does not mix with water. For water-based formulations, you need DME or a compressed gas instead.
Best Applications for LPG
- Air fresheners (alcohol-based)
- Insecticides (solvent-based)
- Spray paints
- Automotive lubricants and degreasers
- Industrial cleaners
DME (Dimethyl Ether)
DME is the second most common liquefied propellant. Its key advantage over LPG is water solubility — it mixes with both water and oil-based formulations.
When to Choose DME Over LPG
- Water-based products: If your formulation is primarily water (many modern air fresheners, fabric refreshers), DME is the right choice.
- Foaming products: DME produces excellent foam structure for shaving creams, hair mousses, and tire cleaners.
- Fine mist for water formulas: DME + water produces a finer spray than compressed gas + water.
DME-Specific Considerations
- More aggressive to some seal materials than LPG — PTFE seals recommended
- Higher cost than LPG (approximately 1.5-2×)
- Also flammable — same explosion-proof requirements as LPG
- Lower pressure than LPG at room temperature — may need higher fill ratio
Compressed Gases (N₂, CO₂, Compressed Air)
Compressed gas propellants are non-flammable and environmentally benign. Their main limitation is the declining pressure curve: as the can empties, pressure drops and spray quality deteriorates.
Nitrogen (N₂)
- Inert: No chemical reaction with product — ideal for oxygen-sensitive formulations
- Primary propellant for BOV: In Bag-on-Valve systems, N₂ or compressed air squeezes the inner bag — the propellant never contacts the product
- Pressure: Typically charged at 8-12 bar. Requires higher-pressure can specifications
Carbon Dioxide (CO₂)
- Partially soluble: CO₂ dissolves slightly in water-based products, providing some pressure maintenance as the can empties (better than N₂, not as good as LPG)
- Not suitable for alkaline products: CO₂ forms carbonic acid in water — can alter product pH
- Lower cost than N₂
Compressed Air
- Essentially free: Generated on-site with an oil-free compressor and filtration
- Requires BOV: Can only be used with Bag-on-Valve packaging — the propellant never contacts the product
- Moisture sensitivity: Requires desiccant drying to prevent water vapor entering the can
Best Applications for Compressed Gas
- BOV cosmetics (sunscreens, facial mists, thermal waters)
- BOV pharmaceuticals (saline sprays, wound care)
- Food-grade aerosols (cooking oils, whipped cream)
- Products marketed as “VOC-free” or “non-flammable”
- Products for markets with strict VOC regulations (California, EU)
Equipment Implications
| Equipment | LPG/DME Required | Compressed Gas Required |
|---|---|---|
| Gas Filler | Liquefied gas filler (e.g., FD9402) | Compressed gas filler (e.g., FD9401A) or BOV system |
| Booster Pump | Yes — FD9405 for propellant transfer | No — cylinder regulator sufficient |
| Electrical | Explosion-proof (Zone 1 / Class I Div 1) | Standard industrial |
| Storage | External cage/structure, 5-15 m from production | Standard cylinder storage |
| Ventilation | 12+ air changes/hour + gas detection | Standard ventilation |
Making the Decision: A Simple Framework
- Is your product water-based? → DME (if you need fine spray) or compressed gas + BOV (for premium positioning)
- Is your product oil/solvent-based? → LPG (best cost-performance)
- Do you need a “non-flammable” or “VOC-free” claim? → Compressed gas, must use BOV packaging
- Are you producing for the EU or California market? → Check VOC regulations — may restrict or prohibit LPG
- What is your budget for facility safety? → LPG/DME adds $10,000-20,000+ for explosion-proof electrical and gas detection
Can’t decide? Many manufacturers start with LPG (lowest per-can cost) and add a compressed gas/BOV line later for premium or regulated-market products. The two systems can operate in the same facility with proper segregation.