# Revisions to Reference Method for the Determination of Fine Particulate Matter as PMINF2.5/INF in the Atmosphere > **Rule** · Direct final rule. · Published 1999-04-22 · Effective 1999-06-21 · 64 FR 19717 ## Document - **Document number:** 99-9593 - **Category:** air-emissions - **Federal Register citation:** 64 FR 19717 - **CFR reference:** 40 CFR 50 - **Publication date:** 1999-04-22 - **Effective date:** 1999-06-21 - **EPA docket:** AD-FRL-6326-5 ## Abstract A new national network of fine particulate monitors is being established over the next two years. In order to assure that monitoring data are of the highest quality and are comparable both within and between air monitoring agencies, many specific design and performance requirements were detailed in 40 CFR part 50, appendix L. Other requirements were set forth in documents such as section 2.12 of the ``Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II, Ambient Air Specific Methods,'' EPA/600/R-94/038b. This direct final action revises two requirements for measurement of fine particulates in 40 CFR part 50. For transport of exposed filters from the sample location to the conditioning environment, 40 CFR part 50 will no longer specify that the protective shipping container be made of metal. For verification of sampler flow rate, 40 CFR part 50 will now specify that new calibrations shall be performed if the reading of the sampler's flow rate indicator or measurement device differs by more than 4 percent or more from the flow rate measured by the flow rate standard. The flow rate verification tolerance was previously set at 2 percent. EPA is publishing this rule without prior proposal because the Agency views this as a noncontroversial amendment and anticipates no adverse comments. However, in the proposed rules section of this Federal Register publication, EPA is publishing a separate document that will serve as the proposal to revise two requirements for measurement of fine particulate in 40 CFR part 50 should adverse comments be filed. ## Source - [Federal Register document](https://www.federalregister.gov/documents/1999/04/22/99-9593/revisions-to-reference-method-for-the-determination-of-fine-particulate-matter-as-pminf25inf-in-the) --- *AI Analytics · CC0 1.0*