ASI Standards Blog

EPA Tier 3 Burning Question Series - Question 1 - Ongoing Precision?

Written by Chris Carolan | Feb 21, 2017 4:09:49 PM

Today we are talking about precision testing under Tier III.

The most common question were face is:

Once I do my precision test under Tier III, are there any ongoing precision requirements? Or is it just one and done?

The answer is YES, there ongoing precision requirements, but to what extent? The EPA has submitted a possible revision to this requirement that can be found in EPA Docket EPA-HQ-OAR-2016-0041…which is only 1200 PAGES LONG!!!

Unless you work in D.C., you are probably not used to reading that many pages. Me either! Starting with a review of the current language, here is the nitty gritty found on pages 103-119:

80.47 Performance-based Analytical Test Method Approach.

(b)Precision and accuracy criteria for approval for the absolute fuel parameter of gasoline sulfur.

• (1) Precision. Beginning January 1, 2016, for motor vehicle gasoline, gasoline blendstock, and gasoline fuel additives subject to the gasoline sulfur standard at §§80.195 and 80.1603, the maximum allowable standard deviation computed from the results of a minimum of 20 tests made over 20 days …taken from a single homogeneous commercially available gasoline … The 20 results must be a series of tests with a sequential record of analysis and no omissions.

(n) Accuracy and Precision Statistical Quality Control (SQC) Requirements for the Absolute Fuel Parameters

• (2)(i) Precision SQC. Every facility shall conduct tests of every instrument with a quality control material as defined in paragraph 3.2.8 in ASTM D6299 either once per week or once per every 20 production tests, whichever is more frequent. The facility must construct and maintain an “I” chart as described in section 8 and section A1.5.1 and a “MR” chart as described in section A1.5.4. Any violations of control limit(s) shall be investigated by personnel of the facility and records kept for a period of five years.
Nothing exciting there, but what about the proposed revision?

The proposed revised language added to 80.47(n)(2)(i):

• The test facility’s long term site precision standard deviation, as demonstrated by the “I” chart and “M” chart, must meet the applicable precision criterion as described in paragraph (b)(1) or (c)(1) of this section.

Whoa! Is this just clarifying the phrase “violations of control limit(s)” or do we have to start conducting 20 test studies at regular intervals? Hopefully the EPA will clarify if this revision is implemented. Similar language can be found for the method-based parameters. For up-to-date clarifications and to stay abreast of other Tier 3 news, follow our blog.

Cheers!

Chris