Understanding Emissions: Start with the Fundamentals

Whether you’re new to emissions, taking on new responsibilities, or simply refreshing your understanding, it’s easy to focus on regulations, testing requirements, or retrofit technologies first.

Those topics matter. But according to GMRC Subject Matter Expert Hans Mathews, they’re easier to understand once you have a solid grasp of the fundamentals.

Physics governs everything about emissions. Once you understand those principles, the rest becomes applying them to real-world engineering problems.

That perspective provides a practical starting point for engineers at every stage of their careers.

Why Start Here?

When engineers encounter an emissions challenge, the natural instinct is often to look for a solution.

• Should the engine be retrofitted?
• Will changing the controls solve the problem?
• What technology should be considered?

Those are important questions. But before answering them, it helps to understand what’s happening inside the combustion process.

That begins with understanding how emissions are formed, what influences their formation, and how engineering decisions can affect the outcome.

Those fundamentals provide a foundation for evaluating the options that follow.

1. How Emissions Are Formed

Every combustion process produces emissions.

Before worrying about regulations or retrofit technologies, take time to understand why emissions are created in the first place. In natural gas engines, that means understanding what happens during combustion and how changes in the air-fuel mixture affect emissions formation.

Hans points to the difference between rich-burn and lean-burn operation as one example. Rich-burn engines operate near a stoichiometric air-fuel mixture, while lean-burn engines operate with significantly more air. That difference changes the combustion process and the emissions it produces.

Understanding those relationships provides context for interpreting operating conditions, test results, and why emissions performance can vary from one application to another.

2. What Influences Emissions Formation

The next step is understanding what influences emissions.

Emissions performance is affected by a combination of operating conditions and engineering decisions. Depending on the application, engineers may need to evaluate factors such as:

• Air-fuel ratio
• Combustion characteristics
• Engine operating conditions
• Ignition energy
• Control strategies
• Equipment configuration

These factors interact within the combustion process. Understanding those relationships helps engineers interpret emissions performance and recognize why results can vary from one engine or operating condition to another.

3. How Emissions Can Be Controlled

Understanding what influences emissions helps engineers evaluate what can be changed to achieve the required result.

No single solution works for every engine or application. The appropriate approach depends on the equipment, operating conditions, performance objectives, and regulatory requirements.

Depending on the application, engineers may consider:

• Air-fuel ratio control
• Ignition system improvements
• Combustion controls
• Catalyst technologies
• Engine modifications
• Other retrofit approaches

The governing physics remain the same, but how those principles are applied will vary. The goal is to understand the problem well enough to determine which approach makes sense for that specific application.

Don’t Let the Science Intimidate You

One of Hans’ most practical pieces of advice is also one of the most encouraging: Don’t be intimidated by the math or the science.

Engineers have already been introduced to the principles that govern emissions. Concepts like conservation of mass, energy, and momentum don’t disappear after college—they simply show up in new ways as engineers solve real-world combustion challenges.

The more you understand those fundamentals, the easier it becomes to tackle increasingly complex problems.

Build Your Expertise

College provides an important foundation, but developing expertise in emissions happens over time.

As regulations evolve, technologies improve, and operating conditions change, engineers benefit from continuing to build their knowledge. GMRC provides research and educational opportunities that help engineers deepen their understanding throughout their careers.

Whether you’re strengthening your understanding of emissions or exploring a specific challenge, you can continue learning through:

• Technical papers and research
• Training courses and workshops
• Gas Machinery Conference (GMC) presentations and short courses
• Regulatory updates and industry insights

The deeper your understanding of the fundamentals, the better equipped you are to apply them to increasingly complex engineering problems. The applications may change, but the physics behind them does not.

Continue building that understanding at the 2026 Gas Machinery Conference, October 4–7 in Indianapolis, where emissions and regulatory compliance are among this year’s technical program tracks.

Build Your Emissions Expertise at GMC

About the Subject Matter Expert

This article draws on insights Hans shared as part of GMRC’s Subject Matter Expert Knowledge Transfer initiative.