Assist Gas Cost & Selection Guide
Choose the right assist gas for your application and optimize costs
Oxygen (O2)
Best For:
Mild steel, carbon steel
Advantages:
- Can enable higher cutting speeds in many setups
- Often lower unit gas cost (for example, $0.10-0.30/m3 in some markets)
- Exothermic reaction adds heat
Disadvantages:
- Oxidized (black) edges
- Not suitable for stainless/aluminum
- Requires post-processing for painted parts
Nitrogen (N2)
Best For:
Stainless steel, aluminum, brass, copper
Advantages:
- Clean, oxide-free edges
- Often reduces or removes post-processing
- Suitable for painted/coated parts
Disadvantages:
- Higher unit cost in many contracts (for example, $0.50-2.00/m3)
- May require slower feeds than O2 at similar edge quality
- Typically run at elevated assist gas pressures (for example, 12-20 bar)
Air (Compressed)
Best For:
Thin mild steel (<3 mm), general purpose
Advantages:
- Lowest cost (compressor only)
- Suitable for non-critical parts
- No gas supply needed
Disadvantages:
- Limited thickness capability
- Moderate edge quality
- Requires oil-free compressor
Cost Comparison by Application
| Application | Recommended Gas | Cost per Hour | Notes |
|---|---|---|---|
| Mild Steel (structural) | Oxygen | $0.50-1.50 | Fastest, lowest cost |
| Mild Steel (for painting) | Nitrogen | $2.00-5.00 | Clean edges, no grinding |
| Stainless Steel | Nitrogen | $3.00-6.00 | Required for quality |
| Aluminum | Nitrogen | $2.50-5.00 | High pressure needed |
| Thin sheets (<3 mm) | Air | $0.20-0.50 | Compressor cost only |
Costs in this table assume bottled gas delivery and are illustrative only. On-site generation can reduce effective nitrogen unit cost in many scenarios; actual savings depend on your equipment, tariffs, and utilization.
On-Site Nitrogen Generation
When does it make sense to invest in your own nitrogen generator?
Bottled Nitrogen Costs
Generator Investment
Planning Tip: Shops with sustained nitrogen usage sometimes find that on-site generation becomes cost-effective over time. Use your own hours of nitrogen cutting, gas and electricity rates, and generator quotes as inputs to an ROI or energy-cost calculator to estimate payback and long-term savings instead of relying on a single rule-of-thumb threshold.
Flow & Pressure Reference
Keep conversion factors handy when translating supplier data.
Common conversions
- 1 bar = 14.5 psi (12 bar nitrogen = 174 psi).
- m3/hr = SCFH x 0.472; SCFH = m3/hr x 2.12.
- kg/cm2 roughly equals bar for quick mental math.
Validate flow references when comparing European spec sheets to US pricing.
Setup checklist
- Log gas purity (99.5%+ for stainless) and dew point (-40 C or better).
- Confirm regulator Cv and hose ID match the required flow rate.
- Record nozzle size/focus inside your processing parameter sheet for repeatability.
Gas Cost Optimization Tips
1. Choose the Right Gas for Each Job
Do not use expensive nitrogen when oxygen will work. For structural mild steel parts that will be painted, the oxidized edge gets covered anyway. Save nitrogen for stainless, aluminum, and parts requiring clean edges.
2. Optimize Gas Pressure
Excessive pressure can waste gas without improving cut quality. Start from your machine or supplier recommended pressure, then adjust in small steps while checking edge quality and cut stability. Use flow meters or supplier guidance to understand how changes in pressure affect actual gas use for your setup.
3. Fix Leaks Promptly
Even small leaks in your gas system can accumulate into meaningful annual cost. Check connections regularly with leak detection spray and use your own gas pricing to estimate the financial impact. Common leak points include quick disconnects, regulators, and nozzle seals.
4. Consider Bulk Gas Delivery
If your nitrogen consumption is consistently high, bulk liquid delivery may offer lower unit pricing than high-pressure cylinders. Discuss volume tiers, tank requirements, and long-term pricing with your gas supplier rather than relying on a single bottle-per-week threshold.
5. Use Air for Non-Critical Parts
For thin mild steel prototype parts, test pieces, or internal brackets, compressed air can provide acceptable quality at minimal cost. Invest in an oil-free compressor with adequate CFM.
Cost Workflow Checklist
Tie gas pricing to the calculators so every quote reflects real consumption.
- 1. Capture contract pricing. Store cylinder rental, delivery fees, purity, and pressure requirements inside your sourcing log so operators and estimators share the same assumptions.
- 2. Convert to hourly cost. Feed flow (m3/hr) and price per m3 into the Hourly Rate calculator or Energy reference to keep shop-rate math aligned with energy usage.
- 3. Push per-part cost downstream. Apply the hourly gas cost inside the Laser Cutting calculator or Price per Meter tool so final quotes show true margin impact.