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 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 fully conforms to the requirements of the EPA Protocol program, in compliance, with the Clean Air Act.