Date: September 24, 2015 

To: Sharon Nizich, EPA/OAQPS/SPPD 

From: Gabrielle Raymond and Kristin Sroka, RTI International 

Subject: Comparison of PM Data for BSCP Tunnel Kilns With and Without Fabric Filters 

I. Introduction 

In accordance with section 112 of the Clean Air Act (CAA), the U.S. Environmental 

Protection Agency (EPA) established national emission standards for hazardous air pollutants 

(NESHAP) on May 16, 2003 for the brick and structural clay products (BSCP) manufacturing 

industry. The NESHAP regulated emissions of hydrogen fluoride (HF), hydrogen chloride (HCl), 

and particulate matter (PM)—a surrogate for hazardous air pollutant (HAP) metals—from tunnel 

kilns located at BSCP facilities. On March 13, 2007, the D.C. Circuit Court vacated the emission 

standards for BSCP manufacturing due to issues associated with the methodology used to 

determine the minimum regulatory “floors” for new and existing units.1 Therefore, on December 

18, 2014 the EPA proposed new standards for BSCP manufacturing, including standards for HF, 

HCl, chlorine (Cl2), mercury (Hg), and non-Hg HAP metals (or PM surrogate). The EPA 

provided a 90-day public comment period following proposal of the BSCP Manufacturing 

NESHAP, during which all affected parties were given the opportunity to comment on the 

proposed rule. The EPA has considered the comments received and, as appropriate, incorporated 

them into the final rule. 

The objective of this memorandum is to compare the PM data for BSCP tunnel kilns with 

fabric filter (FF)-based air pollution control devices (APCD) to the PM data for uncontrolled 

kilns and kilns with other types of APCD. 

II. Analysis 

In other source categories, the EPA has found that as a group, FF-based APCD, including 

dry injection/fabric filters (DIFF), dry lime scrubbers (DLS) with FF, and stand-alone FF are 

better performers in terms of controlling PM emissions than non-FF-based APCD such as dry 

limestone adsorbers (DLA), wet scrubbers (WS), and spray dryer/electrostatic precipitators 

(SD/ESP), as well as uncontrolled kilns. 

 

1 Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007). 
To evaluate whether this observation applies to BSCP tunnel kilns as well, we used a box 

and whisker plot, which is a statistical test for plotting data. We created one box and whisker plot 

for all the PM data from FF-based APCD and another plot for all the other APCD and 

uncontrolled kilns and compared the plots to each other. The box is made up of three points, 

Quartile 1 (Q1), Quartile 2 (Q2), and Quartile 3 (Q3). Twenty five percent of the data lie 

between the minimum data point and Q1. Fifty percent of the data lie between Q1 and Q3, which 

is referred to as the Interquartile range (IQR). Twenty five percent of the data lie between Q3 and 

the maximum data point. The Minimum Whisker is equal to the minimum data point. The 

Maximum Whisker is equal to the maximum data point. Table 1 displays the values graphed in 

the Figure 1 box and whisker plots for the two sets of data by APCD group. 

Table 1. Parameters of Box and Whisker Plots 

Parameter Kilns with FF-based APCD Kilns with Other APCD or Uncontrolled 

Minimum Whisker 0.0076 0.0128 

Q1 0.0184 0.0960 

Median 0.0426 0.1781 

Q3 0.0764 0.3770 

Maximum Whisker 0.2397 1.1877 

IQR 0.0579 0.2810 

Mean 0.0587 0.2754 

Figure 1. Box and Whisker Plots of BSCP Tunnel Kiln PM Data by APCD Group 

0.0

0.2

0.4

0.6

0.8

1.0

1.2

FF‐based Other APCD/ Uncontrolled

Average PM for each kiln (lb/ton)

Mean
Overall, the range of data for the kilns with FF-based APCD is smaller than the range of 

data for the kilns with other APCD and uncontrolled kilns. However, one limitation of this 

analysis is lack of data on all BSCP tunnel kilns, particularly several kilns with DIFF. One kiln 

with a DIFF but with no PM test data is located at Brampton Bricks, Inc., which is an addition to 

the inventory since proposal. In addition, some of the quality assurance/quality control (QA/QC) 

checks described in Test Data Used in BSCP Manufacturing Final Rule (Raymond, 2015), 

particularly the evaluation of EPA Method 5 probe and filter temperatures, resulted in the 

removal of some PM test data on tunnel kilns with DIFF. Therefore, we cannot say with certainty 

that the kilns with FF-based APCD represent the best performers.

III. References 

Raymond, G. 2015. Test Data Used in BSCP Manufacturing Final Rule. Memorandum from 

Gabrielle Raymond, RTI International, to Sharon Nizich, EPA/OAQPS/SPPD. September 24, 

2015.