Protocols 101: Protocol Basics

Getting back to basics with EPA protocol gases

Based on questions and concerns from customers like you, we have gathered useful information here in one place to help you better understand EPA protocol gases.

What makes a gas an EPA protocol gas?

There is more to EPA protocol gases than your average gas mix. You must consider accuracy, traceability and more when measuring for emissions.


Talk to an Airgas specialist about achieving cleaner air, regulatory compliance and more.


Talk to an Airgas specialist about achieving cleaner air, regulatory compliance and more.

  • EPA protocol gases are manufactured and analytically certified in strict accordance with the most recent EPA traceability guideline document entitled EPA Traceability Protocol for Assay and Certification of Gaseous Standards. The majority of EPA protocol gas mixtures from Airgas are certified to a ±1% overall uncertainty guarantee, except where limited by the higher uncertainty of the NIST Standard Reference Materials (SRMs) or NIST Traceable Reference Materials (NTRMs). All analytical certifications are performed under completely interference-free conditions. Maximum allowable shelf life is guaranteed. Documentation (Certificate of Analysis) fully conforms to the requirements of the EPA protocol program, in compliance with the Clean Air Act.

    Metrology Standards Traceability Hierarchy

    Have a question? Ask an Airgas specialist.

How do you pick the right EPA protocol gas and supplier?

Picking the right protocol gas doesn’t have to be complex. Check out How to pick your protocol gas simply and successfully for your application.

What is the worst thing that could happen to your EPA protocol gas?

It used to be that the worst thing that could happen to an EPA protocol gas was that the gas expired, then you were automatically at risk for being out of compliance. Luckily, today’s EPA protocol gases have updated and longer gas shelf lives, making expiration less likely to impact your daily routine. A more probable issue is the risk of an unexpected runout of gas right when you need it or misplacing your certificate of analysis (COA).

  • Airgas offers several solutions that can help you improve cylinder management and avoid misplacing your certificates of analysis (COAs), including the Airgas SRVS app for electronic certificate management as well as stocked EPA protocol gases at your site or within close proximity.

    Have a question? Ask an Airgas specialist.

EPA Instrumental Test Methods

EPA test methods as defined by 40 CFR Part 75 and 60 are used to help you measure pollutants from smokestacks and other industrial sources. Do you know which EPA protocol gas to use for your test method?

How can you tell if your protocol components are compatible?

Ensuring the components of your gas mixture are going to play nicely together is a major concern when you’re working with EPA protocol gases. When they don’t, your mixture will be unstable and ineffective. Mixture components are traditionally classified into two main types: reactive and inert (nonreactive). A reactive component is one that:

  • Exhibits erratic and unstable behavior
  • Presents a significant drop in the expected concentration when blended into a mixture
  • Reacts with other components of the mixture or the balance gas
  • Sticks or attaches to the cylinder wall or delivery system and drops out of the mixture

Conditions like these can lead to unstable mixtures. Airgas utilizes proprietary blending techniques that minimize or compensate for component reactivity, reducing your risk of an unstable mixture and improving the results of your measurements.

What are the keys to cylinder safety?

When gases are a critical component of your daily operations, it’s important to keep cylinder safety at the forefront. Since EPA protocols gases are compressed gases packaged in cylinders under pressure, they are capable of creating hazardous environments for you and your team. No matter how experienced you are, it’s important to review safety hazards and necessary precautions when handling gas cylinders.

What can you learn just by looking at a gas cylinder?

Quite a lot, as a matter of fact. Whether it’s the shape, the color or the numbers on the side, every aspect of a compressed gas cylinder has meaning, and it’s not as hard to decipher as you might think. Find out what it all means by visiting Know Your Cylinder.