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Standard Real-Time Monitor for Particle-Bound
Polycyclic Aromatic Hydrocarbons (PAH)
Since 1991, EcoChem has pioneered the use of the Photoelectric
Aerosol Sensor (PAS) for real-time measurement of particle-bound PAH. Previous
versions of the PAH monitor (PAS 1000i, 1000e and 1002i ) are widely used by
regulatory, research and industrial organizations. Incorporating customer
feedback and state-of-the-art advances in measurement techniques, the PAS 2000
features the following technological advances:
Use of an UV Excimer lamp. This lamp has a higher efficiency than any
traditional UV lamp. The Excimer lamp can be rapidly switched on and off without
a time delay. The offset produced by pre-charged particles can be eliminated by
operating the lamp in a chopped mode.
- The Excimer lamp produces monochromatic radiation with a
half bandwidth of 2%
- Higher sensitivity instrument with a larger measurement
range
- Total microprocessor control with internal data acquisition
and storage
- Lighter and more compact design
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Ambient Air Version
- Outdoor ambient air quality and monitoring in special
settings like parking structures, traffic intersections and motorway tunnels
- Indoor air quality in homes, offices and monitoring indoor
sources like kerosene heaters, wood stoves and environmental tobacco smoke
- Workplace monitoring in industrial environments where PAH
are produced
- Monitoring PAH generation during special situations like
Forest Fires, Scrap Vehicle Tire Fires and Agricultural Burns
Source Emission Version
- Emissions from Combustors, Refinery Heaters, Industrial
Boilers and Furnaces
- Emissions from Municipal, Hazardous and Medical Waste
Incinerators
- Exhausts from Diesel and Gasoline Engines
- Emissions from Industrial Processes like Coke Ovens,
Petroleum Catalytic Cracking, Iron and Steel Foundries, Aluminum and Carbon
Black Manufacture
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- Uses patented Excimer Lamp technology to detect
particle-bound PAH continuously in real-time
- Responds to ultrafine respirable particles which act as
carriers of PAH into the body
- Measures 3 or more ringed PAH which are predominantly
adsorbed on particles and also pose the maximum health risk
- Sensitive in the nanogm/m3 range
- Simple, reliable, field-rugged and proven technology
- Automated operation requiring minimum human intervention.
Built-in data acquisition for 2500 data points.
- Proven source monitoring with special dilution sample
system.
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The Photoelectric Aerosol Sensor (PAS) works on the principle
of photoionization of particle-bound PAH.
- Using an Excimer lamp the aerosol flow is exposed to UV
radiation. The Excimer lamp offers a high intensity, narrow band source of
UV radiation. The wavelength of the light is chosen such that only the PAH
coated aerosols are ionized, while gas molecules and non carbon aerosols
remain neutral.
- The aerosol particles which have PAH molecules adsorbed on
the surface emit electrons which are subsequently removed when an electric
field is applied.
- The remaining positively charged particles are collected on
a filter inside an electrometer, where the charge is measured. The resulting
electric current establishes a signal which is proportional to the
concentration of total particle- bound PAH. Also by operating the Excimer
lamp in a chopped mode, the PAS 2000 can eliminate the back-ground signal
which is sometimes found very close to combustion sources.
The analyzer signal is a measure of total PAH
adsorbed on carbon particles and does not speciate the sample. 
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Source-specific calibration curves are available or can be
generated where the monitor output is compared to an analytically determined PAH
concentration. A site-specific calibration curve can provide greater accuracy
for the particle size, charge and PAH distribution specific to the source.
In addition to the site-specific curves, an approximate universal calibration
curve can be used for screening and real-time trending applications. There is a
approximate relationship between the charge and the total particle-bound PAH
which is independent of the type of aerosol, within a factor of two.
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A specially designed sample conditioning system is available
for monitoring PAH in source emissions. It consists of a heated probe and a
dilution system. These features permit the PAS 2000 to handle emission streams
with high particle loading from stacks. The PAS 2000 can also be connected
to Rotating Disk Dilution System.
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Housing Options The ambient air PAS 2000 can have the
following housing options:
- Standard desktop unit
- Rack-mount unit
- Wall-mounted installation
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115 volts AC / 60 Hz &
220 volts AC / 50 Hz, Max. power consumption 35VA
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2500 Data Points (each
data point consisting of : Date, Time, Value )
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User-friendly
PC-compatible graphical software collects data from PAS 2000. The
software displays real-time strip charts and calculates averages. Data
is stored in a variety or formats. Flat ASCII file output can also be
generated for further analysis in standard spreadsheet programs (e.g.
Microsoft Excel).
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Sampling System
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The standard PAS 2000 can
be modified to include a sample conditioning system. The heated probe
can sample source gas temperatures in the range of 40 to 570 ºF (5 to
300ºC). Using a mass-flow controller coupled with a critical orifice,
it is possible to obtain dilution ratios of 0.05, 0.1 and 0.2.
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Data Acquisition Software
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User-friendly
PC-Compatible graphical software collects data from PAS 2000. The
software displays real-time strip charts and calculates averages. Data
is stored in a variety of formats. Flat ASCII file output can also be
generated for further analysis in standard spreadsheet programs (e.g.
Microsoft Excel).
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