Dusts, Fumes and Fibres

Question 1

Aerosols

Answer 1

A suspension of solid particles and/or liquid droplets in a gas

Question 2

Dusts

Answer 2

Solid materials of varying sizes

Question 3

Fumes

Answer 3

Produced when solid is heated until gas is generated and re-condenses into solid or liquid particles

Question 4

Fibres

Answer 4

Solid thread like filaments with defined length to width ratio

Question 5

Mists

Answer 5

liquid droplets aerosols formed by condensation or atomisation

Question 6

Sprays

Answer 6

Liquid droplets formed by mechanical breakup of a liquid

Question 7

Particle Size

Answer 7

Many classifications of particle size:

• coarse, fine, ultrafine
• PM10, PM25, PM
• inhalable, thoracic, respirable
• nanoparticles

Question 8

50% Cut-Point

Answer 8

The size of dust that device collects with 50% efficiency
Describes the performance of cyclones and other particles size selective devices
Particles smaller than 50% CP collected with efficiency greater than 50%
Particles larger than 50% CP collected with efficiency less than 50%
Inhalable Mass Fraction: 50% CP = 100 um
Respirable Mass Fraction: 50% CP = 4um

Question 9

Particle Size Distribution

Answer 9

Particle size determines:

• length of time dust remains suspended
• way particles will settle
• air speed necessary for particles to be removed by exhaust ventilation

Question 10

Gravitational Settling (Sedimentation)

Answer 10

Inhaled particles settle under gravity within the tracheo-bronchial tree
- larger particles heavier, settle higher

Question 11

Impaction

Answer 11

Particles with mass have inertia when they move at certain velocity in airways. At bends in air passages, they collide with walls and stick

Question 12

Interception

Answer 12

Determined by particle size. Approaches wall of air passage, makes contact and lodges

Question 13

Defence Mechanisms

Answer 13

Entrance to nasal cavities lined with hairs, rest lined with mucous membranes, ciliated mucous secreating cells

Question 14

Fibrogenic Dusts

Answer 14

Cause permanent changes or destruction to alveolar structures, lead to permanent fibrosis

Question 15

Non-Fibrogenic Dusts

Answer 15

Dusts that don’t cause Pulmonary Fibrosis of the lung, physical impairment or disease/disability

Question 16

Silica

Answer 16

Common mineral in the Earth’s crust comprised of Silicon (Si) and Oxygen (O) combined to form Silicon Dioxide (SiO2)

Question 17

Asbestos

Answer 17

Naturally occurring, mined, fibrous silicate mineral with various competitions and structures

Question 18

Sampling Pumps

Answer 18

Flowrates between 0.5-5.0 L/min

Question 19

Filter Collection

Answer 19

Filters: used as a collection medium
Analysis:
- Gravimetric analysis
- Counted
- Dissolved and analysed as a chemical sample

Question 20

Inhalable Dust

Answer 20

INHALABLE FRACTION: contains all sizes of particles that can be inhaled
Materials that are hazardous when deposited anywhere in the respiratory tract
Meet inhalability criterion when personal sampler gives same measured dust concentration and aerodynamic size distribution as inhaled by wearer
50% Cut-point = 100 microns
Measurement methods:
- IOM sampling head
- UKAEA 7-hole sampling head
Flow rate = 2 L/min

Question 21

Respirable Dust

Answer 21

RESPIRABLE FRACTION: separates unwanted material using a miniature cyclone separator prior to filter (removal larger particles)
Flowrates:
- SKC Cyclone = 2.2 L/min
- Aluminium cyclone = 2.5 L/min