1. Chemical and Biological Hazards

2. Gases and Vapors
Gases and vapors are common chemical hazards present in occupational settings.
The difference between a gas and a vapor is the state of the chemical at normal temperature and pressure (NTP).
A gas is in the gaseous state at NTP.
A vapor is in the liquid state at NTP.
Understanding the properties of gases and vapors is important for controlling exposures.

3. Gases
Some common gases and their vapor pressures and vapor densities are as shown below:
Chemical
Vapor Pressure (21.1°C)
Vapor Density
Ammonia
6,658 mm Hg
0.6
Arsine
11,362 mm Hg
2.7
Acetylene
32,838 mm Hg
0.9
Carbon Monoxide
26,600 mm Hg
0.97
Note the high values for vapor pressure for gases. Compare these values to the values for vapors on the next slide and for the values chemicals that do not readily release vapors at NTP (non-volatile liquids) on slide #4.
If you look at the vapor densities you can see that some gases are heavier than air (vapor densities greater than 1), and some gases are lighter than air (vapor densities less than 1). The vapor density is independent of vapor pressure.

4. Vapors
Some common vapors and their vapor pressures and vapor densities are as shown below:
Chemical
Vapor Pressure (21.1°C)
Vapor Density
Acetone
190 mm Hg
2.0
Benzene
80 mm Hg
2.8
Methyl ethyl ketone
2.4
Ethyl Alcohol
65 mm Hg
1.6
Note the values for vapor pressure for gases. Compare these values to the values for gases on the previous slide. You can see that the vapor pressures for these compounds are much lower than the vapor pressures for gases.

5. Non-Volatile Liquids
Some common liquids and their vapor pressures and vapor densities are as shown below:
Chemical
Vapor Pressure (21.1°C)
Vapor Density
Sulfuric acid
0.001 mm Hg
3.4
Hydrogen peroxide
17 mm Hg
1.1
Propylene glycol
0.1 mm Hg
2.6
N-Butyl alcohol
9 mm Hg
Note the values for vapor pressure for these liquids. Compare these values to the values for gases and vapors on the previous slides. You can see that the vapor pressures for these compounds are much lower than the vapor pressures for gases or vapors.

6. Aerosols
Aerosols are generally produced by some activity at a workplace.
An understanding of the properties of the different types of aerosols can help the industrial hygienist in anticipation, recognition, evaluation, and control.
The categories of aerosols are as shown below:
Dusts
Mists
Fogs
Fibers
Smokes
Fumes

7. Dusts
Dusts are typically generated by an action that disturbs a solid material.
Some typical dusts that are present in occupational settings and the source of those dusts are shown in the chart below.
Compound
How Dust can be Generated
Crystalline silica dust (quartz, cristobalite)
Cutting granite
Grinding sand castings
Sand blasting
Mining
Hard wood dust
Woodworking activities
Construction projects
Coal dust
Power generation

8. Mists
Mists are typically produced by some action that disturbs a liquid.
Some typical mists that are present in occupational settings and the source of those mists are shown in the chart below.
Compound
How Mist can be Generated
Acid mist (sulfuric, nitric, hydrochloric)
Steel pickling operations
Mineral oil mist (metal working fluids)
Metal working
Ink mist
Printing

9. Fogs
Fogs are liquid droplets like mists but with smaller average particle sizes. Fogs are generally formed on purpose to saturate an area with a compound.
Some typical fogs that are present in occupational settings and the source of those fogs are shown in the chart below.
Compound
How Fog can be Generated
Methyl bromide
Pesticide fumigation
Propylene glycol
Artificial fog generation for firefighter training and theatrical productions
Mineral oil (fog-oil smoke)
Fog used for military training exercises

10. Fibers
Fibers are particles with a specific length-to-width ratio. Exposures typically occur as a result of disturbing a material.
Some typical fibers that are present in occupational settings and the source of those fibers are shown in the chart below.
Compound
How Fibers can be Generated
Asbestos
Disturbing building materials
Fiberglass
Disturbing insulation
Synthetic fibers
Manufacturing clothing

11. Smokes
Smokes are mixtures of liquid and solid aerosols and sometimes vapors and gases.
Some typical smokes that are present in occupational settings and the source of those smokes are shown in the chart below.
Compound
How Smokes can be Generated
Tobacco smoke
Smoking
Biological smoke
Laser surgery
Diesel exhaust
Incomplete combustion

12. Fumes
Fumes are small aerosolized particles produced by condensation of an aerosolized solid.
Some typical fumes that are present in occupational settings and the source of those fumes are shown in the chart below.
Compound
How fumes can be Generated
Metal fumes
Welding
Soldering
Brazing
Asphalt fumes
Paving
Roofing
Paraffin wax fumes
Food preparation