# Title 40

## SECTION 1065.659

### 1065.659 Removed water correction.

§ 1065.659 Removed water correction.(a) If you remove water upstream of a concentration measurement,
*x*, correct for the removed water. Perform this correction
based on the amount of water at the concentration measurement,
*x*H2O[emission]meas, and at the flow meter, *x*H2Oexh,
whose flow is used to determine the mass emission rate or total
mass over a test interval. For continuous analyzers downstream of a
sample dryer for transient and ramped-modal cycles, you must apply
this correction on a continuous basis over the test interval, even
if you use one of the options in § 1065.145(e)(2) that results in a
constant value for *x*H2O[emission]meas because *x*H2Oexh
varies over the test interval. For batch analyzers, determine the
flow-weighted average based on the continuous *x*H2Oexh values
determined as described in paragraph (c) of this section. For batch
analyzers, you may determine the flow-weighted average
*x*H2Oexh based on a single value of *x*H2Oexh determined
as described in paragraphs (c)(2) and (3) of this section, using
flow-weighted average or batch concentration inputs.

(b) Determine the amount of water remaining downstream of a
sample dryer and at the concentration measurement using one of the
methods described in § 1065.145(e)(2). If you use a sample dryer
upstream of an analyzer and if the calculated amount of water
remaining downstream of the sample dryer and at the concentration
measurement, *x*H2O[emission]meas, is higher than the amount
of water at the flow meter, *x*H2Oexh, set
*x*H2O[emission]meas equal to *x*H2Oexh. If you use a
sample dryer upstream of storage media, you must be able to
demonstrate that the sample dryer is removing water continuously
(*i.e., x*H2Oexh is higher than *x*H2O[emission]meas
throughout the test interval).

(c) For a concentration measurement where you did not remove
water, you may set *x*H2O[emission]meas equal to
*x*H2Oexh. You may determine the amount of water at the flow
meter, *x*H2Oexh, using any of the following methods:

(1) Measure the dewpoint and absolute pressure and calculate the amount of water as described in § 1065.645.

(2) If the measurement comes from raw exhaust, you may determine the amount of water based on intake-air humidity, plus a chemical balance of fuel, intake air, and exhaust as described in § 1065.655.

(3) If the measurement comes from diluted exhaust, you may determine the amount of water based on intake-air humidity, dilution air humidity, and a chemical balance of fuel, intake air, and exhaust as described in § 1065.655.

(d) Perform a removed water correction to the concentration measurement using the following equation:

[73 FR 37335, June 30, 2008, as amended at 76 FR 57462, Sept. 15, 2011; 79 FR 23804, Apr. 28, 2014]