Transcript Gilian-Sampling-Accessories

Air Sampling Accessories
Types of Sampling Accessories

Filters

Sorbent Tubes

Cyclones & Impactors

Impingers

Gas Sampling Bags
Filters are Used to Collect Many
Types of Samples

Dust & Respirable Dust

Asbestos

Silica

Heavy Metals
– Examples: Lead, Chromium,
Cadmium

Alkaline Dusts
There are Many Different Types

Conductive

2 part or 3 part

MCEF

PVC

PTFE

37mm or 25mm

Gridded

Banded
Filter Sampling Methods

Sampling methods are
published by NIOSH, OSHA
and EPA that will describe the
type of membrane used.

The sample flow rate will also
be described in the sampling
method, along with
information on run time.

Filter sampling methods are
normally run with high flow
personal monitoring pumps in
the range of 1 to 4 LPM.
Criteria Identifying Filter Membranes

Diameter in mm

Pore size in microns (µm)

Material

Example: 37mm, 5 µm, PVC
There are Many Types of Filter
Media
◉ MCE or MCEF: Mixed cellulose ester fiber
◉ PVC: Polyvinyl chloride
◉ PTFE: Polytetrafluoroethylene (Teflon)
◉ Glass Fiber
◉ Polycarbonate
A Filter Membrane May be Plain or
Gridded

Grid lines are often
preferred for microscopic
analysis

Grid lines may be offered in
different colors
The Filter Cassette May Have
Further Description
◉ Two-Piece: Cassette consists of two press-fit parts
◉ Three-Piece: Cassette includes a center ring to allow
open-face sampling
◉ Conductive: Will not build static charge
◉ Banded: Has shrink band around press joint for
tamper seal
Asbestos Filters May be Described
by the Test Method

PCM: Phase Contrast
Microscope analysis
specified in the OSHA and
NIOSH methods

TEM: Transmission Electron
Microscope analysis
specified in the EPA-AHERA
test method
Filter Assembly

Three piece cassette: inlet is
at top

Center ring allows open face
sampling

Support pad beneath filter

Filter and pad lay on
vacuum disperse grid
Most Popular Filters
Filter Type
Sample For
37mm, 5µ, PVC
Dust, Silica, Hex Chrome
37mm, 0.8µ, MCE
Lead, Cd, Chromium
25mm, 0.8µ, MCE
Asbestos PCM
25mm, 0.45µ Polycarbonate or MCE
Asbestos TEM
Sorbent Tubes
Sorbent Tube Basics

Sorbent tubes are designed to
collect airborne gases and vapors.

They work because the target
gases adhere to the surface of the
collection media.

They are designed for low flow
rates, usually between 20 and
200 cc/minute.

The target gas is recovered in the
lab by desorption, either
chemical or thermal.
Types of Sorbent Tubes

Many types of materials have
been applied to sorbent tubes.

Most have been borrowed
from gas chromatograph
technology. Examples are
Tenax, Porapack and XAD.

However, the most popular
type of sorbent tube contains
activated charcoal.
Sorbent Tube Design

A sorbent tube is usually
made in two layers of
unequal size.

The sample is collected in a
large layer, and a smaller
layer serves to determine
breakthrough.

An arrow indicates direction
of air flow.
Most Popular Sorbent Tubes
Filter Type
Application
Activated Charcoal
Hydrocarbon solvents, alcohols, acetates,
ketones, methylene chloride, benzene
Washed Silica Gel
Acid gases
Silica Gel
Amines
XAD-2 (Hydroxymethyl
Piperidine
Formaldehyde, aldehydes
Cyclones & Impactors

Cyclones and impactors are
used ahead of filters to
provide particle size selection.

Cyclones use centrifugal force
to remove large particles.

Impactors use small
passageways to remove large
particles, and can be multilayered.
Cyclones and Impactors
Applications
◉ Cyclones provide respirable dust samples (e.g., lung
penetrating particles).
◉ Cyclones are suitable for sampling for inert dusts
and silica dusts.
◉ Impactors can provide for PM-10 and PM-2.5 air
sampling.
Impingers

Impingers allow air
sampling with a liquid
capture media.

An older technology, most
impinger methods have
been replaced by sorbent
tube methods.
Types of Impingers

Standard impingers have a
tapered end on the internal
delivery tube.

Bubblers have a fritted end
to provide many smaller
bubbles, increasing the
contact surface area.
Impingers

Standard impingers require
a special bracket to mount
them to the pump.

Impingers are still used for
monitoring for isocyanates
like TDI, and sometimes for
formaldehyde.
Spill Proof Impingers

Special spill proof impingers
are available for
convenience, but they are
not specified in the test
methods.
Bag Sampling

Certain gases are collected
in special sampling bags.

From there they can be
detected in a laboratory or
with a portable gas monitor.

The bag sampling allows an
8 hr time weighted average.
Bag Sampling

The bags are made of
special inert materials like
Teflon® and Kynar®

Tedlar®, a popular sampling
material has been pulled off
the sampling bag market by
the supplier.
Bag Applications

Carbon dioxide

Ethylene oxide

Nitrous oxide

Sulfur Hexafluoride

Trichloroethylene
Thank you
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