The document summarizes guidance from the U.S. EPA Region 6 on calculating hourly averages from continuous emissions monitoring systems (CMS) data and reporting CMS downtime. The EPA guidance clarifies that using the average of 4 quarter-hour periods to calculate an hourly average is improper, and the average should instead use all valid 1-minute data points from the full hour. The guidance also changes the method for determining reportable CMS downtime, defining it as any period where valid data is not collected for more than 40% of the hour. The impacts of this new guidance include changes to compliance determination, enforcement procedures, data acquisition and handling system vendors, and reporting procedures.

1. www.all4inc.com
Impacts of U.S. EPA Region 6
Guidance on CMS Downtime
and Data Calculations
Eric Swisher | eswisher@all4inc.com | 610-422-1117

2. 2 Your environmental compliance is clearly our business.
Typical CMS Diagram
Sample
Conditioning
SystemProbe
Assembly
Data
Acquisition
& Handling
System
Analyzers
Sample
Pump
Calibration
Gases
Sample Line
Instrument
Air

3. 3 Your environmental compliance is clearly our business.
CMS Sampling Frequency
❑ 40 CFR §60.13 (e) – …all continuous monitoring
systems shall be in continuous operation and shall
meet minimum frequency of operation
requirements as follows: [40 CFR §60.13
(e)(1)&(2)]
❑ 40 CFR §60.13 (e)(2) - All continuous monitoring
systems shall complete a minimum of one cycle
of operation (sampling, analyzing, and data
recording) for each successive 15-minute period.

4. 4 Your environmental compliance is clearly our business.
❑ 40 CFR §60.7 (b) – …Any owner or operator
subject to the provisions of this part shall
maintain records of the occurrence and duration
of any startup, shutdown, or malfunction in the
operation of an affected facility; any malfunction
of the air pollution control equipment; or any
periods during which a continuous monitoring
system or monitoring device is inoperative.
CMS Downtime

5. 5 Your environmental compliance is clearly our business.
Compliance Demonstration
Build Base
Average
Excluded from
Compliance
Demonstration
Reportable CMS
Downtime
Measured
CMS Data
Validation
Compliance
Demonstration
Calculation
Unable to Demonstrate
Compliance in Terms of
the Emission Standard
Express in Terms of
the Emission Standard
Good Bad
Hourly
Average
CMS
Bad
Good
Compliance
Average
Validation
Good
Bad

6. 6 Your environmental compliance is clearly our business.
1-hour Block Average Validation
❑ Full Operating Hour [§60.13(h)(2)(i)]
❑ Partial Operating Hour [§60.13(h)(2)(ii)]
❑ Maintenance or Quality Assurance Hour [§60.13(h)(2)(iii)]

7. 7 Your environmental compliance is clearly our business.
1
23
4
0
15
30
45
1-hour Block Average Validation
❑ …1-hour averages shall be
computed as follows…for a
full operating hour (any
clock hour with 60 minutes
of unit operation), at least
four valid data points are
required to calculate the
hourly average, i.e., one
data point in each of the 15-
minute quadrants of the
hour. [§60.13(h)(1) & (h)(2)(i)]

8. 8 Your environmental compliance is clearly our business.
U.S. EPA Region 6 Guidance
❑ April 18, 2017 – ODEQ requested clarification
from U.S. EPA Region 6 on:
1. Reporting of CMS Downtime
2. Calculation of an Hourly Average
❑ June 26, 2017 – U.S. EPA Region 6 responded to
ODEQ (in coordination with OECA & OAQPS)

9. 9 Your environmental compliance is clearly our business.
The unit operated the entire hour, and there was no required maintenance or quality assurance activity conducted in this hour.
Hourly Validation Example
Minute Value
0 2
1 2
2 3
3 2
4 3
5 2
6 PURGE
7 PURGE
8 PURGE
9 PURGE
10 3
11 4
12 3
13 3
14 3
Minute Value
15 4
16 PURGE
17 PURGE
18 PURGE
19 PURGE
20 4
21 25
22 35
23 30
24 25
25 5
26 PURGE
27 PURGE
28 PURGE
29 PURGE
Minute Value
30 2
31 3
32 4
33 2
34 3
35 3
36 PURGE
37 PURGE
38 PURGE
39 PURGE
40 3
41 2
42 3
43 2
44 2
Minute Value
45 4
46 PURGE
47 PURGE
48 PURGE
49 PURGE
50 4
51 3
52 3
53 4
54 4
55 3
56 PURGE
57 PURGE
58 PURGE
59 PURGE
1 2 3 4
Average 2.73
Valid 12
Invalid 4
Quadrant Valid
Average 18.29
Valid 7
Invalid 8
Quadrant Valid
Average 3.57
Valid 7
Invalid 8
Quadrant Valid
1
23
4
0
15
30
45
Average 2.64
Valid 12
Invalid 4
Quadrant Valid

10. 10 Your environmental compliance is clearly our business.
Current:
❑ Can a compliance average
be calculated?
❑ Reportable CMS
Downtime?
U.S. EPA Region 6 Guidance:
❑ Can a compliance average
be calculated?
❑ Reportable CMS
Downtime?
Hourly Validation Example
YES
0 Hours or 0 %
YES
24 Minutes or 40 %
1
23
4
0
15
30
45

11. 11 Your environmental compliance is clearly our business.
Compliance Demonstration
Build Base
Average
Excluded from
Compliance
Demonstration
Reportable CMS
Downtime
Measured
CMS Data
Validation
Compliance
Demonstration
Calculation
Unable to Demonstrate
Compliance in Terms of
the Emission Standard
Express in Terms of
the Emission Standard
Good Bad
Hourly
Average
CEMS
Bad
Good
Compliance
Average
Validation
Good
Bad

12. 12 Your environmental compliance is clearly our business.
U.S. EPA Region 6 Guidance
❑ April 18, 2017 – ODEQ requested clarification
from U.S. EPA Region 6 on:
1. Reporting of CMS Downtime
2. Calculation of an Hourly Average
❑ June 26, 2017 – U.S. EPA Region 6 responded to
ODEQ (in coordination with OECA & OAQPS)

13. 13 Your environmental compliance is clearly our business.
ODEQ Request – Hourly Averages
❑ Hourly average based on:
• 4, 15-minute quadrant averages collected during a
clock hour OR
• 60, 1-minute averages collected during a clock hour
❑ U.S. EPA Region 6 Response
❑ Using the quadrant average “appears to be improper
data reduction”

14. 14 Your environmental compliance is clearly our business.
The unit operated the entire hour, and there was no required maintenance or quality assurance activity conducted in this hour.
Hourly Validation Example
Minute Value
0 2
1 2
2 3
3 2
4 3
5 2
6 PURGE
7 PURGE
8 PURGE
9 PURGE
10 3
11 4
12 3
13 3
14 3
Minute Value
15 4
16 PURGE
17 PURGE
18 PURGE
19 PURGE
20 4
21 25
22 35
23 30
24 25
25 5
26 PURGE
27 PURGE
28 PURGE
29 PURGE
Minute Value
30 2
31 3
32 4
33 2
34 3
35 3
36 PURGE
37 PURGE
38 PURGE
39 PURGE
40 3
41 2
42 3
43 2
44 2
Minute Value
45 4
46 PURGE
47 PURGE
48 PURGE
49 PURGE
50 4
51 3
52 3
53 4
54 4
55 3
56 PURGE
57 PURGE
58 PURGE
59 PURGE
1 2 3 4
Average 2.73
Valid 12
Invalid 4
Quadrant Valid
Average 18.29
Valid 7
Invalid 8
Quadrant Valid
Average 3.57
Valid 7
Invalid 8
Quadrant Valid
1
23
4
0
15
30
45
Average 2.64
Valid 12
Invalid 4
Quadrant Valid
Methodology Average
4, 15-min Quadrant 6.81
All valid minutes 5.89

15. 15 Your environmental compliance is clearly our business.
Additional Impacts
❑ Compliance
❑ Enforcement
❑ DAHS Vendors
❑ Reporting Procedures

16. 16 Your environmental compliance is clearly our business.
Questions?
Eric Swisher
Technical Manager
(610) 422-1117
eswisher@all4inc.com