Basic Properties of Air & Airborne Contaminants (Module 3) Flashcards
What are the types of airborne contaminants?
- Gases and vapors
- Aerosols
What state are gases in at room temp?
Gases are in a gaseous state at room temperature
What state are vapors in at room temp?
Vapors can be either solids or liquids at room temperature
What is airborne behavior for gases and vapors influenced by?
density differences (vs air) and temperature, leading (possibly) to possible buoyancy effects
What are aerosols?
Liquid or solid particles suspended in air
What is airborne behavior for aerosols influenced by?
Airborne behavior influenced by inertia, gravity, diffusion, and (sometimes) electrostatic effects
What are examples of respiratory hazards?
- Oxygen deficient atmospheres
- Hazard of airborne contaminants (aerosols, gasses, and vapors)
- Some toxic aerosols or gases do not affect the lung tissue locally, but have adverse effects on other body organs or on the oxygen-carrying capacity of the blood cells
What is the upper respiratory tract composed of?
- nose
- pharynx
- larynx
What do the middle and lower respiratory tracts consist of?
- trachea
- all segments of the bronchial tree
- the alveoli
What does the aerodynamic sizes determine?
Where the particles are deposited in the respiratory tract
How do gases absorb and deposit in the respiratory tract?
- Very water-soluble gaseous chemicals may only reach the upper respiratory tract.
- Less water-soluble gaseous chemicals may reach the lower respiratory tract.
How do aerosols absorb and deposit in the respiratory tract?
- Large particles can only deposit in the upper respiratory tract.
- Small particles can reach the lower respiratory tract.
What are the emission sources for aerosols/particulates?
- mechanical actions
- chemical actions
What is the basic form of gases?
molecules mix with air and diffuse to (eventually) fill the space containing them
What is the basic form of vapors?
gaseous emissions from liquid surfaces – molecules escape
EX: boiling liquids, cold liquids in open-top containers, airborne droplets
What is vapor pressure?
- Influences the tendency of liquid molecules to escape from the liquid surface and become vapor in the air
-high vapor pressure → more volatile
What is volatility (vapor pressure)?
-tendency to evaporate
What are the critical exposure factors for gases and vapors?
- Concentration
- Exposure time
- Mode of use and potential for exposure
- Temperature and volatility
- Reactivity
What are examples of aerosols?
- Dust
- spray
- mist
- fume
- smoke
- bioaerosol
What is dust? (aerosol)
- solid particles made airborne by mechanical disintegration of solid material
- sub-μm to over 100 μm
What is spray? (aerosol)
- large liquid droplets produced by mechanical disruption of bulk liquid
- sub-μm to up to about 40 μm
What is mist? (aerosol)
- finer liquid droplets produced during condensation or atomization
- sub-μm to a few μm
What is a fume? (aerosols)
- small solid particles produced by condensation of vapors or gaseous combustion products (primary particles), usually followed by coagulation (aggregates)
- up to about 1μm
What is smoke? (aerosol)
- small particles produced by incomplete combustion, usually in the form of aggregates following condensation and coagulation
- up to about 1μm
What is a bioaerosol? (aerosol)
- solid or liquid particles consisting of, or containing biologically- viable organisms (viruses, bacteria, allergens, fungi, etc.)
- sub-μm up to 100 μm
What are some examples of aerosols in the workplace?
- Cutting or extraction of bulk solid mineral material (e.g., coal, ore, etc.)
- Cutting (or otherwise working/machining), handling, conveying solid material (e.g., bulk chemicals production, agriculture, etc.)
- Milling, smelting or refining (e.g., metals primary production)
- Textiles production (e.g., batching, carding, spinning or weaving)
- Welding, soldering, brazing, etc.
Does a bigger or smaller particle settle faster?
Bigger, smaller stays suspended for longer
What is problem characterization?
Study of emission sources, worker behavior, and air movement
What are controls for problem characterization based on?
emission sources, air movement, and worker behavior
Problem Characterization in Predesign Phase: Emission Source
- Location of emission sources
- Which emission sources and in what ratios actually contribute to exposure
- Characterization of each source: chemical composition, temperature, rate of emission, direction of emission, initial emission velocity, continuous of intermittent, time intervals of emission
Problem Characterization in Predesign Phase (Air)
- Air temperature
- Air movement
- Mixing potential
- Supply and return flow conditions
- Air changes per hour
- Effects of wind speed and direction
- Effects of weather and season
Problem Characterization in Predesign Phase (Worker)
- Worker interaction with the emission source
- Worker location
- Work practice
- Worker education, training, cooperation
