From: <Myers.Ron@epamail.epa.gov>

To: jimn@esclabs.com

CC: Segall.Robin@epamail.epa.gov; Parker.Barrett@epamail.epa.gov; 

Westlin.Peter@epamail.epa.gov; Joe.Fanjoy@erg.com; Danny.Greene@erg.com; . . .

Date: 7/8/2009 7:21 PM

Subject: Re: CPM method question

Jim:

First an appology for a somewhat late response or an appology for a

second response should I have already responded to this question.

The purpose of the divided box with somewhat different temperature

requirements is to minimize the potential to form sulfate artifact in

the first two impingers and to maximize the collecteion of water vapor

for calculating the moisture content of the sampled gas.

If you do not mind the increased potential to form sulfate artifact in

the first two impingers, you can put the first two impingers in the same

box or part of the box for the impingers that are intended to collect

water vapor passing through the first two impingers and the back up

filter. The temperature at the exit of the back up filter will be much

lower than 85F and satisfy the requirements of the method.

In the stakeholder process to develop the method, there were two

considerations for selecting the temperature level. The first

consideration was the desire to minimize sulfate artifact formation.

Environment Canada provided information that the solubility of SO2 in

water was greater at lower temperatures. Decreasing the solubility of

SO2 reduces the quantity of SO2 that can oxidize to SO3 where it can not

be removed with the nitrogen purge. The second consideration was the

desire to establish a collection temperature that is consistent and is

representative of ambient temperature. In the use of another sampling

method that is based upon the dilution of the sampled gas with filtered

and conditioned ambient air during a hot humid day, we were only able to

reduce the filtration temperature to 85F. This is a temperature that is

reasonable as an ambient temperature level and is near the standard

temperature and within the normal 25F range for maintaining temperature

for stack sampling. Also, this somewhat elevated temperature addresses

concerns that the promulgated Method 202 condenses organic and inorganic

vapors greater than would be consistent with ambient temperatures of

about 35 to 40F. The dilution in ambient air would further reduce the

solid concentrations of these compounds. The combination of the lower

temperature and the lack of dilution would tend to provide a high bias

to the particulate matter collected. This information is documented in

the running commentary on the method development that is in the docket

and on the FAQ page for Method 202

( http://www.epa.gov/ttn/emc/methods/method202.html#af ).

Let me know if you have additional questions.

_________________________________

Ron Myers

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

Sector Policy and Programs Division

Monitoring Policy Group, D243-05
RTP NC 27711

Tel. 919.541.5407

Fax 919.541.1039

E-mail myers.ron@epa.gov

-----"Jim Narens" <jimn@esclabs.com> wrote: -----

To: Ron Myers/RTP/USEPA/US@EPA

From: "Jim Narens" <jimn@esclabs.com>

Date: 07/07/2009 04:36PM

Subject: CPM method question

Ron,

I was hoping you could clear some confusion I have with this method.

Looking over this method, it seems to be vague about the specifics of

the temperature of the external filter and how it is achieved.

I know that it is stated in Section 8.5.1 to “maintain the CPM filter

≤ 30oC(≤ 85oF) during sample collection”. Figure 1 in

Section 18 it is clearly shown to be two sections in the cold box

portion of the train.

Why is this?

The iced portion of the box (back half), used to drop out any remaining

moisture, will be below 68 oF. Does this not satisfy the condition of

being ≤ 30oC (≤ 85oF)? Could we not simply use a non-divided

box and circulate the ice water through our condenser to achieve a

filter temperature of ≤ 30oC (≤ 85oF)? The entire premise of

the method deals with this condensation temperature of 85oF. Any gas

passing through the train less than 68 oF will more than satisfy this

condition. Again, why have two separate temperature requirements when 68

oF is obviously ≤ 30oC (≤ 85oF)?

Thank you for any insight you can provide.

Jim

James A. Narens, III jimn@esclabs.com

E nvironmental S ervices C ompany , Inc.

13715 W. Markham

Little Rock , Arkansas 72211

ph. # 501-221-2565 ext. 122

fax # 501-221-1341

www.esclabs.com