Overview

Over the last decade the components of the

air that we breathe have been the subject of

a great deal of scientific research and 

environmental regulation. No longer is the

mass of particles in the air the primary 

concern, but instead it is the species or 

elements that make up those particles that

are important to understand. In the United

States, the Clean Air Act (CAA) currently

requires the U.S. Environmental Protection

Agency (EPA) to regulate the emissions of

188 toxic air pollutants from industrial

sources referred to as “source categories.”

To accomplish this, the EPA chose the

Maximum Achievable Control Technology

(MACT) standards for each source category.

The CAA also requires that the EPA assess

the residual health risks from the source 

categories using MACT standards.

Problems with Conventional

Monitoring Technologies

Currently, the regulatory methods being used

to identify air pollutants are performed manually

once every three-to-six days. With these

methods, air is pulled through a filter for 

24 hours and then the filter is removed and

shipped to a laboratory for analysis. Data is

recorded and is put through a quality 

assurance protocol, and is then reported

back to the technician where the samples

were taken. This process typically takes a

few weeks to complete.

There are challenges with this type of air 

monitoring system – challenges that are 

common regardless of where the regulatory

stations are placed in service. The first major

challenge is that the number of metals that

can be monitored is limited by the cost 

associated to sample and analyze the filters.

This typically does not allow regulators the

ability to monitor all of the metals that they

would like to monitor in an effort to protect

public health and public welfare. A second

challenge is that a sample is collected over a

24-hour period of time. This long duration for

sample collection cannot provide regulators

with critical and specific information on where

and when the metal arrived to the monitor.

Finally, the delay between the day that the

sample is taken and when the metals 

concentration is reported is problematic in itself.

This type of monitoring and reporting system

does not provide regulators with near-real-time

data which could be used to immediately

inform the public of unhealthy air conditions.

As an alternative, a high-resolution, multi-metal

monitor is recommended to provide regulatory

Pall Xact1 625 Series Systems Provide Near-Real-Time

Monitoring of Multi-Metals 

1 Xact is a trademark of Cooper Environmental Services

LLC.
investigators with near-real-time data to 

characterize complex airsheds. The ability to

provide near-real-time data is essential to

advance monitoring to meet today’s needs.

The challenge is how to increase the frequency

and diversity of the data available so that the

location and time of the most dangerous

metal emissions can be identified. 

Pall Xact 625 Series

Monitoring Systems

Pall Xact 625 Series monitoring systems are

based on X-Ray Fluorescence (XRF) technology.

XRF technology was selected as an analytical

method for use in this application for its 

long-term stability and multi-metal analysis

capability. When XRF technology is combined

with a reel-to-reel tape drive sampler, multimetals can be monitored in near-real-time,

with data being reported in time periods as

short as 15 minutes.

Pall Xact 625 Series systems are designed 

to monitor ambient air near “fence lines” of

industrial facilities and in complex urban 

environments, where particulate matter and

metal concentrations may be at elevated levels.

Features and Benefits

• Sampling, analysis, and near-real-time

reporting 

• Detection limits as low as 10 pg/m3

• Automatic quality assurance, alarms and

control features

• Identification and measurement of up to 

24 elements simultaneously

• Capable of identifying hazardous “hot

spots” around the perimeter of a facility 

• Highly sensitive and reliable (low pg/m3 to

μg/m3 range) 

• Non-destructive analysis allows for 

sample archiving 

XRF Technology Overview

XRF technology has been utilized in the 

scientific research community for more than

50 years. Xact monitoring systems, using XRF

technology, have been successfully installed

for over 10 years. The same technology has

been approved by the U.S. EPA for compliance

on Hazardous Waste Incinerators for the past

six years. 

Recent Successes

In 2007, the first XRF ambient multi-metal

monitor was introduced to the U.S. EPA,

which began a three-year feasibility study. In

2010, after a full evaluation of the system, the

U.S. EPA purchased its first mobile, multi-metal

monitoring lab. The mobile lab was first

deployed in the investigation of elevated 

metal concentrations surrounding certain 

U.S. schools.

Around the same time that the U.S. EPA was

testing the XRF monitor, the South Korean

government began the procurement of Pall

Xact systems for their Super Site project. This

was a four-year project to build five Super Site

labs to characterize multi-metal pollutants

from long transport emissions.

Most recently, the Chinese government 

purchased Pall Xact 625 Series systems for

the characterization of multi-metal pollutants.

The systems were placed in several major

cities – Chongqing, Suzhou and Beijing. Six

more cities within China have been authorized

to procure Pall Xact ambient systems. The

systems will be used to research, identify, and

better understand the current metals baseline

so that appropriate regulatory limits can be

established.

The Xact 620 can

provide hourly

concentration

results for multiple

metals with an

uptime that is

equal to or better

than a Federal

Reference Method

(FRM) sampler,

stability equal to

that expected from

laboratory XRF 

analysis, and 

one-hour detection 

limits up to 10 times

lower than those

attainable with a

24-hour FRM 

sampler with 

laboratory XRF

analysis.

U.S. EPA sponsored study2

2 U.S. EPA study, Field Bias and Precision Demonstration

of a Near-Real-Time Multi-Metals Ambient Fence Line

Monitor, December 2009. EPA Contract EP-D-05-096.

Power Generation

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Because of technological developments related to the products, systems, and/or services

described herein, the data and procedures are subject to change without notice. Please

consult your Pall representative or visit www.pall.com to verify that this information

remains valid.

© Copyright 2012, Pall Corporation. Pall and are trademarks of Pall Corporation. 

® Indicates a trademark registered in the USA. and ENABLING A

GREENER FUTURE are service marks of Pall Corporation. 

PGABX625EN Produced in the USA February 2012