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CIH > Air Sampling & Instrumentation > Flashcards

Air Sampling & Instrumentation Flashcards

1
Q

Absorption

A

The removal of gaseous constiutent from a gas stream by pentration of the gas molecules into a liquid or solid matrix. Needs bubbling to achieve good mixing.

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2
Q

Properties/Types of Absorption Sampling

A

Properties
- Low volatility, low viscosity, low foaming, non flammable

Types
- Fritted Glass (MFGB), Impinger (MI)

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3
Q

Adsorption

A

The removal of gaseous constituents from an airstream by a solid matrix in which the gas molecules are deposited on the surface of the adsorbent

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4
Q

Factors affecting adsorption

A
  • Nature of material (surface area, polarity, reactivity, etc.)
  • Temperature
  • Velocity of air stream
  • Concentration of gases
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5
Q

Active adsorption

A

air pulled thru tube
Break-thru criteria for chemical sampling media
NIOSH > 10% on back up
OSHA > 25% on back up section
―Migration – diffusion of sample from front to rear over storage time
5% on pre/post calibration of pumps = bad sample
Field Blanks: 10% of sample, Minimum 2

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6
Q

Passive adsorption

A

relies on molecular diffusion (ficks first law)
Critical Air Velocity 0.2 m/sec
Performance affected by: Face velocity, temperature, humidity, pressure, and reverse
diffusion

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7
Q

Common adsorbents

A
  • activated charcoal
  • silica gel
  • porous polymers
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8
Q

Conductivity:

A

Gases form electrolytes in solution and change conductivity of solution (NH3, SO2)

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9
Q

Potentiometry:

A

Gases react with reagents to change pH of solution (O2, CO, H2S)

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10
Q

Coulometry:

A

measurement of the number of electrons transferred across a solution/electrode interface

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11
Q

Flame ionization:

A

measurement of conductivity of gas as a result of ionization of gas by flame (total Hydrocarbons)

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12
Q

Thermal conductivity:

A

resistance of heated filament changes with temperature changes of filament caused by thermal conductance of gas flowing over filament (wheatstone bridge)

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13
Q

Fume

A

Solid particles formed by condensation after heating (0.001-0.2 m)

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14
Q

Dust

A

Solid particles formed by mechanical processes (0.5-50 m)

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15
Q

Mist

A

A dispersion of liquid particles (40 - 400 m)

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16
Q

Smoke

A

Solids from incomplete combustion

17
Q

Fog

A

Liquid formed by condensation

18
Q

Fiber

A

aspect ration of 3-1

19
Q

Aerosol behavior effected by

A

1) size
2) shape
3) density
4) Hygroscopic

20
Q

Stokes Law (particle settling rate)

A

Vs = 0.003SGd2(cm) Or Vs = 0.006 x SG x d2 ( m)

Terminal settling velocity is proportional to d2

21
Q

Filter medium - Forces Acting on an Aerosol

A
  • Sedimentation – gravitational effects (based on Stokes Law)
  • Impaction – Rapid changes in Air direction impacts particle on filter
  • Diffusion – Random displacement due to air‘s Brownian Motion
  • Interception – Airflow of particle past a collecting medium 1/2 particle size to be captured by ―touching” electromagnetic attraction (oil wipes this out)
22
Q

Filter medium - Forces promoting

retention

A
  • Van der Waals
  • Electrostatic charge
  • Capillary forces due to liquids
23
Q

Three major types:

A

Filtering, Impaction, and impingement

24
Q

Impingement:

A

not commonly used as a technique anymore

  • Greenberg-Smith: Flow rate 1 cfm, pressure drop 3”Hg
  • Midget impinger: 0.1 cfm,
  • Particle counting - (see Ocular microcopy for more information) Mppcf – million particles/cubic ft (6.4 mppcf = 1 mg/m3)
25
Q

MCEF

A

0.8 m, 37mm & 25 mm used for Not for Gravimetric
855 and 385 mm2 used for Metals, asbestos
100

26
Q

Glass

A

Analytical finish requires strong chemicals
Benzidine, aldrine
32

27
Q

PVC

A

5 m typical, used for gravimetric tests
Dust, Cr (IV)
15

28
Q

PTFE

A

5m typical, used for extraction/desorption
Alkaline dust, formic acid
25

29
Q

Silver

A

Sample support medium for x-ray analysis

2

30
Q

Types of Asbestos

A
  • Amosite
  • Chrysotile - Most Common
  • Tremolite
  • Crocidolite - Blue Asbestos, Most Dangerous
31
Q

Inhailable particulate Mass (IPM)

A

any size within the respiratory tract (up to 100 m) (Inertial Impaction)

32
Q

Thoracic Particulate Mass (TPM)

A

Airway of lungs or gas exchange region (5-15 m) (Top Impaction, bottom diffusion and impaction)

33
Q

Reparable Particulate Mass (RPM)

A

Gas exchange region 5 m, sedimentation or diffusion dependent on size of particle (0.1 m)

CIH (5 decks)

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