evan406's version from 2015-12-09 16:41


Question Answer
How toxicants enter biological organisms (list 4)1. Ingestion – enter through the mouth into the stomach and threat eliminated by enforcement of rules on eating, drinking, and smoking

2. Inhalation – enter through the mouth or nose into the lungs and threat eliminated by ventilation, respirators, hoods, and other PPE

3. Injection – enter through cuts into the skin and threat eliminated by proper protective clothing

4. Dermal absorption – enter through skin membrane and threat eliminated by proper protective clothing
How toxicants are eliminated from biological organisms (list 3)1. Excretion – through kidneys, liver, lungs, or other organs

2. Detoxification – by changing the chemical into something less harmful by biotransformation

3. Storage – in the fatty tissue
TLVThreshold limit value; below this does the body is able to detoxify the body and eliminate the agent without any detectable effects
TLV-CCeiling – The concentration that should not be exceeded during any part of the working exposure
PELPermissible exposure level – PEL values are OSHA’s threshold doses and follow the TLV-TWA very closely. However, the PEL values are not as numerous and are not updated as frequently. TLVs are often somewhat more conservative.


Question Answer
OSHA-PSM – Process Safety Management-On site, for workers
- Sets general requirements for the management of hazardous chemicals
-14 major sections: employee participation. process safety information, process hazard analysis, operating procedures, etc.
EPA-RMP - Risk Management Plan- Off site, for public

- Has the following elements: hazard assessment, prevention program, emergency response program, onsite documentation

- Updated when the process or chemistry changes or when an update is requested
MSDS - Material Safety Data Sheet (list 7)1. Hazardous ingredients/identity information

2. Physical/chemical characteristics

3. Fire and explosion hazard data

4. Reactivity Data

5. Health Hazard Data

6. Precautions for Safe Handling and Use

7. Control Measures
Personal Protective EquipmentThe last line of defense as a part of the chemical plant industrial hygiene methods

Prevents or reduces exposure by providing a barrier between the worker and the workplace environment.
What does bypassing mean in an enclosure?Bypass air is supplied through a grille at the top of the hood. This ensures the availability of fresh air to sweep out contaminants in the hood. The bypass air supply is reduced as the hood sash is opened.
Estimating worker exposure during vessel filling operations. Describe each of the two emission sources. What is the transport phenomena associated with each source (type of fluid, mass and heat transport)?Evaporation of the liquid (heat and mass)

Displacement of vapor in the vapor space by the liquid filling the vessel (mass and fluid)
Air-ventilation in an enclosure; is it needed on the inlet or the outlet or both? Show how it should be done.Air ventilation is need on the inlet and outlet of an enclosure. Air enters the workspace, closer to ground level, and is vented out through a higher point near the ceiling.

Fan should be placed on the exhaust end of the systems because fans create a tiny pressure drop and pulls air out of the system. This ensures that leaks in the system draw air in from the workplace rather than expel contaminated air from the ducts into the workplace.

Ch 4

Question Answer
What is meant by an orifice coefficient or a discharge coefficient?Co, A complicated function of the Reynolds number of the fluid escaping through the leak and the diameter of the hole.

The frictional losses in the leak are approximated by a constant discharge coefficeint

For flowing liquids the kinetic energy changes are frequently negligible and the physical properties are constant

for flowing gases and vapors these assumptions are valid only for small pressure changes (P1/P2 < 2) and low velocities (< 0.3 times the speed of sound in gas)
What is meant by sonic velocity?The velocity of a gas or vapor is the velocity of sound at the prevailing conditions
What is Pchoked? Where is it measured?Choked pressure

It is the maximum downstream pressure resulting in maximum flow through a hole/pipe

Measured at throat


Question Answer
What is a puff?A formation that results from a near instantaneous release of material; shaped a bit like a cloud the moves with the wind
Can you see a puff?You can only see it if the gas/vapor released is visible
Does the puff get more concentrated as it moves downstream?The maximum concentration is always found at the puff center
Where is the isopleth in a puff?The puff isopleth is close to circular as it moves downwind; the diameter of the isopleth increases initially as the puff travels downwind, reaches a maximum, and then decreases in diameter

atmospheric conditions

Question Answer
What combination gives the most mixing in atmospheric conditions?The most mixing occurs with low wind speed, high insolation, in the early hours of the day
Which combination gives the least mixing in atmospheric conditions?The least mixing occurs with high wind speed, low insolation, at night
atmospheric conditions - An example of combination is high wind speed, daytime, and low insolation... does it give the most mixing?No


Question Answer
How are atmospheric conditions quantified in a Pasquill-Gifford Case model?Classified according to 6 different stability classes, depend on wind speed and quantity of sunlight

Applies to only neutrally buoyant dispersion of gases

A = extremely unstable, F = moderately stable (two extremes)
What is the effect of buildings or plant structures on air mixing or the absence of buildings (urban vs. rural)?Trees and buildings increase mixing, whereas lakes and open areas decrease it
What are the advantages and consequences of higher elevation toxicant release (e.g. from flare stacks, vapor emissions from tall distillation columns, etc.)?The release height significantly affects ground-level concentrations

As the release height increases, ground-level concentrations are reduced because the plume must disperse a greater vertical distance

Buoyancy and momentum of the material released change the effective height of the release


Question Answer
What is Insolation?solar input energy
When is Insolation high?Strong insolation corresponds to a sunny midday in midsummer in England
When is Insolation low?Slight insolation corresponds to similar conditions in midwinter
What is meant by atmospheric stability? (Unstable/Stable Air)Atmospheric stability relates to vertical mixing of air

During the day, the air temperature decreases rapidly with height, encouraging vertical motions

At night the temperature decrease is less, resulting in less vertical motion
Unstable (atmospheric conditions)the sun heats the ground faster than the heat can be removed so that the air temperature near the ground is higher than the air temperature at higher elevations; results in instabilities because air of lower density is below air of greater density
Neutral (atmospheric conditions)the air above the ground warms and the wind speeds increases, reducing the effect of solar energy input; the air temperature difference does not influence atmospheric mechanical turbulence
Stable (atmospheric conditions)he sun cannot heat the ground as fast as the ground cools; therefore the temperature near the ground is lower than the air temperature at higher elevations; the influence of buoyancy suppresses mechanical turbulence


Question Answer
ERPGEmergency Response Planning Guidelines (ERPG) – for air contaminants issued by the American Industrial Hygiene Association (AIHA)
ERPG-2the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to one hour without experiencing or developing irreversible or other serious health effects or symptoms that could impair their abilities to take protective action
ERPG-3the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to one hour without experiencing or developing life threatening health effects

Ch 6

Question Answer
What are the elements for combustion?fuel, an oxidizer, and an ignition source
What is fire?the rapid exothermic oxidation of an ignited fuel
When will fire not occur?fuel is not present or is not present in sufficient quantities

an oxidizer is not present or is not present in sufficient quantities

the ignition source is not energetic enough to initiate the fire
Flash point- meaning?the lowest temperature at which it gives off enough vapor to form an ignitable mixture with air

Vapor will only burn briefly because not enough vapor is present to maintain combustion
LFLLower Flammability Limit - The mixture will not burn when the composition is lower than this limit

the mixture is too lean for combustion
UFLUpper Flammability Limit - The mixture is not combustible when the composition is too rich, or above this limit
When is a mixture flammable?A mixture is only flammable when the composition is between the LFL and UFL
Flammability of mixtures containing oxygen and those containing air - are specific mixtures flammable or not?Combustion in pure oxygen also exhibits a lower oxygen limit (LOL) and an upper oxygen limit (UOL), just like the LFL and UFL in air

For most hydrocarbons, the LOL is close to the LFL

A good estimate of the UOL can be found using the UFL
What is the auto-oxidation temperature?The temperature at which liquids begin to oxidize (liquids with relatively low volatility are particularly susceptible to this problem)

Spontaneous combustion is often a result of auto-oxidation

Deflagration index for gases and dusts

Question Answer
What does Deflagration index for gases and dusts mean? Indicates robustness of explosion
What does Deflagration index for gases and dusts depend on?Function of maximum pressure increase and volume

Depend on concentration, mixing, vessel shape, ignition energy
What are the characteristics of dust mixtures that are explosive?the particles must be below a certain minimum size, typically less than 400 microns

the particle loading must be between certain limits

the dust loading must be reasonably uniform


Question Answer
What is the blast wave pressure vs. time?A blast wave is composed of the pressure wave and subsequent wind

The blast wave causes most of the damage

Most damage during shock duration

Strong winds accompany the shock duration
What is meant by TNT equivalence?The estimated overpressure of an explosion is compared to the overpressure resulting from a TNT explosion of a known mass an equal distance from the explosive origin
What does TNT equivalence measure for a compound in a process vessel or a vapor cloud?It is a simple method for equating a known energy of a combustible fuel to an equivalent mass of TNT

The overpressure curve for TNT tends to over-predict the overpressure near the vapor cloud explosion (VCE) and to under-predict the distance away from the VCE
What is the overpressure needed to damage the most sensitive parts of houses?The overpressure needed to damage the most sensitive parts of houses (the windows) ranges from 0.15 to 0.3 psig
What is the overpressure needed to distort steal frames of clad buildings?The overpressure needed to distort steel frames of clad buildings is above 1.3 psig