Gases, Vapors, Solvents & Particulate Matter
Solvents and Solvent Vapors very high concentrations
(1000s ppm), solvent vapors may cause simple asphyxiation. This is most likely to occur in confined spaces.
Solvents and Solvent Vapors high concentrations
(100s ppm), solvents tend to have a rapid effect on the CNS, resulting in dizziness, disorientation, confusion, euphoria, and giddiness. Prolonged exposure at high levels can lead to loss of consciousness, paralysis, convulsion, and ultimately, death.
Particles of dust are respirable when size is
(<10 μm).
Liquid nitrogen
-Wear proper safety gear when handling to prevent contact or inhalation of the extremely cold vapor. -Cover and insulate skin to avoid exposure, Because it boils so rapidly, the phase transition from liquid to gas can generate a lot of pressure very quickly. -Do not enclose liquid nitrogen in a sealed container, as this may result in it bursting or an explosion
Compressed gas cylinders should
-be securely stored with DOUBLE CHAINS to prevent falling and breaking, -be stored in a WELL VENTILATED area, -have SIGNAGE to indicate the potential hazards, -be STORED and TRANSPORTED with cap on to protect valve & be protected from HEAT, which can generate greater pressures inside than the cylinder was designed to withstand (e.g.: in welding Area)
Electrostatic precipitation...
...is also used in some industrial applications. The application of paint/powder coats make use of electrostatic precipitation. The paint is given a charge, and the surface to be coated is given the opposite charge.
Vapor pressure...
...refers to the pressure exerted by a vapor when it is at the same temperature as its condensed phase (liquid or solid)
Vapor pressure..
..depends highly on temperature
Electrostatic precipitation..
..does not appear to be the case in the respiratory tract.
Additive.
.The more closely the PM-related health effects are, the more appropriate it is to judge them to be
Gases.
.are materials that are in the gaseous state at normal temperature (25°C/80°F) and PRESSURE (1 ATM)
Personal sampling.
.assures that the filter goes wherever the worker goes, and collects particles representative of the airborne concentration of PM wherever that employee works.
Interception.
.is most effective for mid-sized particles.
Surface sampling for PM.
.is not needed where the contaminant is of low toxicity, since a visual observation will suffice.
General area sampling.
.is used extensively in specific settings, asbestos abatement in particular/ building maintenance and renovations
Vapor pressure.
.is very temperature dependent as the temperature rises, the airborne concentration of an equilibrium mixture will rise.
Dry swipe sample.
.method is the least reliable method and it is only used to determine type of PM
Wet swipe sample.
.procedure is more reliable than the dry swipe method since it collects all the particles on the surface. The particles concentration is measured by dividing the number of particles by the surface area
Electrostatic precipitation.
.widely used for air pollution control. Some air filters are designed to charge airborne contaminants and/or attract charged particles.
Under EPA fibers must be
> 0.5 micrometer and meet a 5:1 aspect ratio to be counted under the microscope.
Under OSH and NIOSH microscopic counting rules the fibers must be
> 5 micrometer long and have an aspect ratio of at least 3:1 to be counted.
Transient illness
A few hours of overexposure to some metal fumes from welding can result in
Full calibration
A number of commercially available static-type calibration kits are available for commonly measured gases and vapors. These kits usually contain one or more cylinders filled with a known concentration of a specified gas air mixture. Once the kit is attached to the instrument, a sample of the gas air mixture is permitted to flow into the device. The meter reading of the instrument is then compared with the known concentration of the sample to verify proper response.
Volatile
A substance with a high vapor pressure at normal temperatures (room temperature)
Asphyxiation risk
Adding a lot of nitrogen to the air reduces the relative amount of oxygen
Sedimentation (settling)
All particles are acted upon by gravity. If the particle settles onto a surface, it will be removed from the aerosol
Active Method
Also known as personal sampling, assures that the filter goes wherever the worker goes, and collects particles representative of the airborne concentration of PM wherever that employee works
Lead and Asbestos
An example of a non interactive concurrent exposure would be. While they are both primary occupational hazards, their target organs, health effects, and mode of action are very different. When both exposures are measured simultaneously, the results are treated independently, and if both exposures are below the appropriate limits, the operation is in compliance.
Inertial impaction
As a particle moves within an aerosol, it gains momentum. When an aerosol is forced to change direction abruptly, the gas phase does so easily, however, a suspended particle tends to resist the change in direction and deviates from the airstream. This may cause the particle to impact on the surface (e.g., lung, filter) and stick there.
Environmental Justice Movement
As many workplaces that make intensive use of diesel engines are located in economically disadvantaged neighborhoods
Diffusion (Brownian movement)
As the very small (submicron) particles flow with the air, they tend to wander from the airflow lines, and may bump into a collection surface and be removed from the aerosol.
Synergistic combination of toxicants
Asbestos and cigarette: Latency period of mesothelioma for a smoker person who is exposed to asbestos is 10 years instead of 30 years for a non-smoker, Carbon tetra chloride and ethanol, Particulate matters and So2, Ethanol and alcohol will cause immediate nervous system poisoning.
Organic and Inorganic gases can produce a multitude of hazards
Asphyxiants, Acute Toxins, & Chronic Toxins
Examples of biological sampling
Benzene in the urine, Cadmium in the blood and the urine, Lead in the blood
Inorganic Acids and Bases: Strong acids and bases are
CORROSIVE and can burn the skin and mucous membranes.
Electrostatic precipitation
Charged collection surfaces will attract and hold oppositely charged particles. Most airborne particles carry some net charge.
Nature of health problems caused by inhalation of PM is influenced by a number of factors
Chemical Composition, Isotopic Composition, Crystalline and Structural, Shape of Particles, & Size of particles
Amorphous quartz (non crystalline silica)
Chemically identical to quartz and other free crystalline silica, but lacks a fully formed repetitive crystalline structure. (not same shape and structure). As a result of this difference, glass, natural or manmade, is of low toxicity.
Vapors
Chemicals that are liquids at normal temperature and pressure will exist partially in the gaseous phase
Smoke
Consists of carbon or soot particles resulting from the incomplete combustion of materials.
Direct reading indicator tube
Contain chemical reagent that is sealed in glass. The tubes are broken open and the chemical reagents are exposed to the atmosphere that is tested. The airborne contaminants are indicated by a color change caused by chemical reactions between the contaminant and the tube reagent.
Arsenic and cadmium
Diesel smoke can also contain other carcinogenic PM such as:
Solvents and Solvent Vapors low concentrations
Direct contact with the skin can cause irritation, defatting, and dermatitis
Liquid maybe flammable or explosive
Flash point is the lowest temp. at which it gives off enough vapor to form an ignitable mixture with the air near the surface of the liquid or in a vessel.
Fumes
Form when the material from a volatilized solid (e.g., arc welding) condenses in cool air.
DIFFUSION
Gases spread rapidly throughout a room by
Passive method
General area sampling, accomplished by using high volume pumps to move large quantities of air through a filter medium
Upper flammability limit (UFL)
Highest concentration (percentage) of a gas or a vapor in air capable of producing fire in the presence of an ignition source (arc, flame, heat).
Vacuum collection
If dust is visible on the surface, samples can be collected by using a micro-vacuum. The filter cassette is then sent to a laboratory for analysis.
Wet Swipe Sample
In this method, a filter or a swipe tab is pre wetted with water or another liquid prior to use.
Overall deposition is the sum of five primary mechanisms of particle deposition
Inertial impaction, Interception, Sedimentation, Electrostatic Precipitation, Diffusion
Other Chemical Monitoring Instruments
Infrared (IR) analyzers that measure compounds that absorb IR, Flame Ionization detectors (FID) measure a wide variety of chemicals
DPM
It has been shown to be carcinogenic and cause a range of respiratory tract and cardiovascular problems.
Synergistic
It is the situation where the combined effect of two chemicals is much greater than the sum of the effects of each agent given alone, for example: 2 + 2 >> 4 (maybe 10 times or more) Some PM exposures are synergistic.
Aerosols
Liquid droplets or solid particles that fine enough to remain dispersed in air for a prolonged period.
Functional/bump test
Many direct reading instruments require a functional test in situations where frequent confirmation of the sensor's performance is important because of hazardous conditions.
Asphyxiants
Many of these elements and compounds have no or very minimal odor, and thus have poor warning properties.
Inhalation
Most important route of exposure for most particulate matter
Air Sampling
Most samples collected by this technique, particles are removed from the aerosol by filtration, impaction, or electrostatic precipitation. The collected particles then will be analyzed under the microscope
25 ppm
Nitric oxide (NO) has a Threshold Limit Value of
Acute Toxins Delayed
Nitrogen dioxide exerts its effects several hours after exposure.
Surface Sampling
PM from clothing or skin surfaces (collected as an indication of dermal exposure). Commonly used in research on particles that pose substantial transcutaneous hazards (e.g., pesticides).
Aerosols can be classified into two different kids, based on size of particles
Polydesperse and Monodesperse
Isotopic Composition
Radioactive atom.
Electrostatic Precipitator
Radon example sample testing
Examples of antagonistic effects
Snake bite antidotes, Atropine for organophosphate, Dimercaprol for arsenic and inorganic mercury, Activated charcoal for most poisons
Particulate matter (dusts)
Solid particles of minerals or organics generated by handling, crunching, grinding, impact, or detonation.
Acute Toxins Immediate
Some gases (e.g., phosphine, arsine) can cause acute fatalities with short exposures to relatively low concentrations.
Dual phase monitoring
Sometimes you need to sample for particulate matters and gas or vapor at the same time to get an accurate and full understanding of the exposure
Mists
Suspended liquid droplets generated by condensation of liquids from the vapor state or by breaking up a liquid into a dispersed state.
Personal sampling technique is also considered for the
TLV STEL, TLV C, and the Excursion Limit
Interception
The particle follows the airstream fairly well but still makes contact with the surface and sticks.
Particle deposition
The removal of a particle from an aerosol state
Photoionization Detectors
These types of detectors utilize Ultraviolet light (UV) and they are commonly used on hazardous waste sites.
Electrochemical Detectors
They are specific detectors, commonly measure CO, H2S, and O. A chemical reaction creates an electrical current when the gas enters the cell.
Additive
This action occurs when the combined effect of two or more chemicals is equal to the sum of the effect of each agent given alone (they do not interact in a direct way) for example: 2 + 2 = 4
Potentiation
This effect results when one substance that does not normally have a toxic effect is added to another chemical, making the second chemical much more toxic (example: 0 + 2 > 2 (0 has no effect. If we add 0 to 2 then we will create a chemical that has more toxic effect than chemical 2.))
Surface sampling is conducted for several reasons
To determine adequacy and effectiveness of housekeeping controls, To determine adequacy and effectiveness of engineered controls, When working on laboratory fume hoods, Prior to releasing excess equipment for reuse, utilization, sale, or donation, When necessary to determine what metals are/were used in an area in the past, Where the contaminant has a high percutaneous toxicity, & Whenever working with radioactive PM.
Chemical Composition
Toxic nature of the particle & Solubility of the particle (e.g., how rapidly is it removed from the body, where in the body is it transported-hydrophilic or lipophilic)
Size of Particles
Toxicity of some agent depends very directly on the size of the individual particles to which people are exposed.
When opening drums of liquids (especially hazardous waste drums)
Use a non-sparking tool (brass), we do not want to increase the temperature. Make sure you don't create friction when opening a waste drum with a low boiling point hazardous substance.
Lift tape
Utilizes pressure-sensitive tape to determine the presence of particulate contamination.
Dermal Exposure
When inhalations exposures are controlled, this may be the major route of entry.
The Excursion Limit
Worker exposure levels may exceed 3 times the TLV TWA for no more than a total of 30 minutes during a workday, and under no circumstances should they exceed 5 times the TLV TWA, provided the TLV TWA is not exceeded. But this is not applicable for STEL.
Gas
a formless fluid that completely fills its container and EXERTS AND EQUAL PRESSURE IN ALL DIRECTIONS.
Asbestos fibers are said to have
a high aspect ratio (length divided by width).
When using direct reading instrumentation,
a much greater number of samples and much more information can be obtained and evaluated.
All substances are poisons, there is none which is not a poison, but the concentration is what differentiates
a poison and a remedy.
Use liquid nitrogen in
a well-ventilated area.
Reactivity of the gas may be important: After the exposure, some of the inhaled chemical compounds react with the moisture of the respiratory system's mucous membrane. This reaction forms
acids and toxic substances that causes irritation to the respiratory system.
Combustible gas indicators require
adequate oxygen to work properly. The instrument will give a false result in oxygen deficient area. Many also include detectors for oxygen or toxic gases.
Monodesperse
aerosols that contain one size partcles. This kind is used in research.
Flammable range includes
all concentrations of vapor in the air that are between the Lower Flammable Limit (LFL) and the Upper Flammable Limit (UFL).
AED value
also determines where the particle size will deposit in the respiratory tract
Flammability: Some gases ignite spontaneously when exposed to air
and cause fire hazard or some time explosion hazard
When both exposures are measured simultaneously the TWA fractions of the respective exposure limits found for each agent are added together
and if the value exceeds 1.0, then an over-exposure situation is assumed to exist.
Flammable range
another factor to rate fire hazard of flammable gas or liquid
Flammable and combustible liquids
are classified according to their flash points and boiling point
Particles making up the fume
are extemely fine (usually < 0.1 μm) and respirable.
Pre Existing Health or Genetic Status: Occupational exposure limits for particulate matter (or other classes of stressors)
are generally set for "healthy" workers.
Most important factors in exposure potential
are how the material is used and what controls (e.g., engineering, PPE) are in place.
Typically, Smoke particles
are less than 0.1 μm in size.
Personal integrated industrial hygiene air samples
are most typically collected onto filters placed in the breathing zone of the worker (within ~9 inches of the nose and mouth) with air drawn through the filter at the rate of 0.5 to 4 liters per minute.
The health consequences of concurrent inhalation of cigarette smoke and asbestos exposure
are much greater than the sum of the parts, on the order of 50-100x. Lung infection and exposure to pneumoconiosis producing dust often seem to act synergistically.
Combustible Gas Indicators (CGIs)
are nonspecific detectors. Each indicator contains a sensor that detects any type of combustible gas or vapor in the working area and then display the present of the Lower Flammable Limit (LFL) of these gases or vapors.
Particulate monitors
are particle counting devices that use laser technology and light scattering principles to count individual particles.
Particles of dust
are respirable when size is (<10 μm) (less than)
Filter cassettes
are used for microscopic fibers.
Combustible liquids
are with a flash point greater than 100 F
A court decision has made it clear that a woman cannot be forcibly discharged or even shifted from one job to another to protect her fetus
as long as her exposure and biological monitoring results fall below the minimum OSHA standards.
Asbestos always has an aspect ratio of
at least 10:1.
Dose (concentration and duration)
at some point,everything becomes toxic.
Crystalline and Structural: For example, the toxicity of silicon depends not on the intrinsic toxicity of the element
but on the types of compounds silicon makes with other elements and their crystalline structure
Some types of PM may be hazardous
by ingestion or skin contact.
From the nasopharyngeal region
by physically by blowing the nose clears the particulate matters from the aerosol in the respiratory system.
From the pulmonary region
by the macrophage (asbestos ruin it), or the lymphatic system clears the particulate matters from the aerosol in the respiratory system.
From the tracheobronchial region
by the muco ciliary escalator mechanism (Mucous) clears the particulate matters from the aerosol in the respiratory system.
Number of samples can be determined
by the number of employees in the working area.
PM that persists in lung tissue for weeks or months may
cause chronic lung disease including lung cancer
Species with high specific activities emit a lot of ionizing radiation per unit time and mass, and thus more rapidly affect tissue
causing genetic and somatic cell damage.
Color badges
change their color to indicate a chemical exposure. Color badges are easy to use and they are usually used for acutely toxic gases.
An instrument's response to a concentration of a substance can shift as a result of a variety of factors
chemical degradation of sensors, physical damage, drift in electronic components, exposure to extreme environmental conditions (e.g., high temperatures), extremely high contaminant exposures, or exposures to poisons or inhibitors.
NIOSH analytical method to sample total elemental carbon is difficult to use in environments where
coal dust or organic dust is also present, as these substances lead to positive interference.
Liquid nitrogen (Cryogenic Liquid)
cold enough to cause severe frostbite upon contact with living tissue.
Confined space combustible gas detectors
contain at least three different sensors for LEL, Oxygen, and toxic gas (Co or H2S)
Polydesperse
contain range of particle size. This kind is very common in the workplace.
Remember that in the UFL atmosphere, ventilation control
could be a bad choice because ventilation will reduce and lower the concentration of the flammable gas and produce a mixture within the flammable range before the safe concentration limit can be reach.
In both air sampling methods, analysis of PM samples
could be by microscopic counting or respirable mass fraction
Slow release
decomposition, rotting
From the point of view of chemical kinetics, reaction rates
depend on some factor of concentration.
Airborne concentration of a solvent vapor
depends on the vapor pressure, which is a measure of the volatility of the solvent.
Respiratory Cancer
deposition of radioactive particles in the lungs presents the risk of.
Temperature
directly related to the vapor pressure of any chemical.
Expanded OSHA standards for PM
do generally require some medical evaluation of workers before significant exposure to a specific PM (e.g., lead, asbestos, cadmium, arsenic).
OSHA in general
does not require pre-exposure medical assessment for workers who will be exposed to hazardous particulates. But, the Expanded OSHA Standards (29 CFR 1910.1001-1052) are an exception to this rule.
Volatile chemicals are a big concern in the field of safety and health
due to the high potential of exposure.
Insoluble PM
either will be cleared from the respiratory tract by the various defenses of the lungs, or may remain in the lungs for an extended period of time
Class IB FL Boiling Point
equal to or greater than 100°F
Class II CL Flash Point
equal to or greater than 100°F, but less than 140°F
Class IIIA CL Flash Point
equal to or greater than 140°F, but less than 200°F
Class IIIB CL Flash Point
equal to or greater than 200°F
Class IC FL Flash Point
equal to or greater than 73°F, but less than 100°F
If a liquid is spilled, some will evaporate and, over time,
equilibrium may be established between the gas and liquid phases.
Bioassays (e.g., blood, urine analysis)
exist for many particulates that provide an indication of actual absorbed dose or biological changes resulting from absorbed dose.
Concurrent Exposure to other Toxic Agents
exposure occurs to more than one type of PM, or PM plus gases, vapors or infectious agents. While in many cases these multiple exposures do not interact, in some cases they may interact additively or synergistically.
The range of PM sizes under consideration is
five orders of magnitude (0.001 μm to 100 μm).
In a comprehensive industrial hygiene program, all women should have their workplace evaluated
for potential exposure to teratogenic or fetotoxic exposures, including radiation exposure when applicable.
Solid particles of minerals or organics
generated by handling, crushing, grinding, impact, or detonation. As used in industry, particulate matter (PM) is used to describe airborne solid particles that-range in size from 0.001 μm to 100 μm in diameter (1 μm = 0.00004 in.)
A liquid at high pressure
has a higher boiling point than when that liquid is at normal atmospheric pressure.
A liquid at low pressure (or in a vacuum)
has a lower boiling point than when that liquid is at normal atmospheric pressure.
Toxicity occurs after the particulate matter
has been removed for the air by deposition in the respiratory tract
DPMs carcinogenicity
has traditionally been ascribed to its high content of polynuclear hydrocarbons, which are known carcinogens.
AED value predicts
how a particle will behave when inhaled or passing through a respirator or sampling filter much more reliably than the actual size of the particle.
Direct read instruments for chemical contaminants
identify and/or quantify the concentration of many gases, vapors, and particulates in air, in real time or near real time.
Effectiveness of sedimentation
in a still aerosol is proportional to the particle's mass, and large particles settle out much faster than small particles.
Keep in mind that particles behave differently in different areas of the respiratory tract
in nasal area, tracheobronchial, and pulmonary region
Sedimentation
in small air ways where velocity of air is low and gravity is considered
Surface sampling for PM
in some workplaces is useful as an adjunct to air sampling. This may include taking wipes of surfaces or sampling from an employee's skin or clothing.
Samples can be collected
in the field and returned to the laboratory for analysis, or they may be collected and analyzed on the spot with direct-reading instrumentation.
Particle deposition happens
in the respiratory tract, on industrial hygiene air sampling filters, and inside filter-bag houses in factories (control method).
Organ systems that are affected by some solvents
include the liver, the kidney, the CNS, and the peripheral nervous system.
Low readings could falsely
indicated that no hazard is present
Substantial exposure to PM can
induce a wide variety of biological responses ranging from acute to chronic, local to systemic, mild to life threatening
pneumoconiosis
insoluble PM result in a type of illness (dust in the lungs). The term has been widely used to describe a number of lung diseases after inhaling particulate matters
Aerosol
is a collection of suspended particles and the surrounding gases.
Pressure sensitive adhesive (PSA) tape
is a continuous flexible strip of cloth, paper, metal or plastic coated on one or both sides with a permanently tacky adhesive at room temperature which will adhere to a variety of surfaces with light pressure (finger pressure) with no phase change (liquid to solid)
Exposure to DPM
is a known occupational hazard to truckers, railroad workers, and underground miners.
Vapor pressure
is a measure of the concentration of the chemical in the air at equilibrium.
Decomposition
is a slow combustion refers to reactions that occur between a fuel and oxidant that accompanied by release of heat and conversion of chemicals.
Diesel particulate matter (DPM)
is a specific form of smoke from the diesel cycle internal combustion of diesel fuels.
Pregnancy
is a temporary medical condition that may predispose either the pregnant woman or her fetus to occupational disease.
General area sampling
is accomplished by using high volume pumps to move large quantities of air through a filter medium, Filters are often stacked to remove progressively finer particles for the sampled air.
Direct measure
is also used widely to measure the flammable level, combustible level, oxygen level, and toxicity level of particles in the working area
Equilibrium vapor pressure
is an indication of a liquid's evaporation rate and relates to the tendency of atoms/molecules of the substance to escape from the liquid (or solid).
Impaction
is most effective for large and dense particles in high-velocity air.
Any concentration that is lower than the LFL
is not sufficient to form an ignitable mixture.
Radon
is one of the noble gases, which generally refuse to react with other compounds and, therefore, are almost always found as gases & is a naturally occurring gas that is usually formed by the radioactive decay of uranium. Even though the gas is radioactive, it is not usually an occupational hazard, as it is not significantly absorbed as a gas when in contact with the surface of the lungs.
Concentrated hydrogen fluoride (HF)
is particularly corrosive to tissue and bone. Serious tissue damage may result without the person being aware of it.
Bump test
is performed by briefly exposing the instrument to a concentration of a substance in excess of the lowest alarm set point for each sensor. If the response of the instrument is within an accepted tolerance, then the calibration is verified.
Lower flammability limit (LFL)
is the lower end of the concentration range over which a flammable mixture of gas or vapor in air can be ignited at a given temperature and pressure. And it is usually 10 %
Class 1A
is the most hazardous because it ignites rapidly due to its low flash point.
Antagonism
is the opposite of synergism. It is the situation where the combined effect of two or more compounds is less toxic than the individual effects for (example: 4 + 6 < 10)
As used in industry, particulate matter (PM)
is used to describe airborne solid particles that range in size from 0.001 μm to 100 μm in diameter (1 μm = 0.00004 in.).
Personal sampling
is used to monitor the average exposure for an individual over an 8 hr working period of time as determined by taking one or more samples during the 8 hr working period (TWA).
Asbestos
is usually fibrous.
Quartz (crystalline silica)
is very toxic to lung tissue.
Dry swipe sample
is when the surface is rubbed with a dry filter or special swipe tab.
Pure silicon
is with a low toxicity when inhaled.
As radon radioactively decays by the release of an alpha particle
it turns first into radioactive polonium
Impaction
large and dense particles/due to high velocity air changing direction
Class IA FL Boiling Point
less than 100°F
Class IA FL Flash Point
less than 73°F
Class IB FL Flash Point
less than 73°F
Rapid release
light is produced (eg: glowing amber, flame)
Silicates
make up the bulk of the earth's crust, and vary in toxicity from very toxic to relatively inert.
Sampling and analysis for DPM poses a range of difficulties. When using standard filter methods
many other dusts can be collected as well, resulting in positive interference.
Silica
may be found or made in both a non-crystalline form (glass), or a crystalline form (quartz).
Chronic inhalation of very fine, respirable particles of quartz
may lead to silicosis.
Skin contact with dusts alone
may result in burns, sensitization, systemic toxicity, or cancer.
Interception
medium size fibers
To be of inhalation concern, a particle must
not be too big, as it would not stay suspended in the air long enough to be inhaled, nor too small, as it then takes on the characteristics of a gas rather than a particle.
Aerodynamic Equivalent Diameter. (AED)
of a particle is the diameter of a unit density sphere that would have the identical settling velocity as the particle of interest
PM that is cleared from the respiratory tract is
often swallowed, giving the material another shot at absorption into the body via the digestive tract.
Shape of Particles
often the defining characteristic that makes a particle toxic.
For a working area that has 7 employees or less
one sample is required for each employee.
At higher concentrations, NO reacts rapidly with
oxygen to produce nitrogen dioxide (NO2), which has a TLV of 3 ppm (proposed to drop to 0.2 ppm).
Spray painting
poses a greater exposure risk for the worker than brush or roller application.
Co exposure to any of the pneumoconiosis
producing dusts, as they produce variably related conditions.
An appropriately selected direct reading instrument may be used to
quickly establish a safe zone around a chemical spill, and are often used to assess the exposure of workers to hazardous chemicals.
Organic Compounds
readily permeate the skin or glove materials.
Reducing concentrations
reduces the potential for exposure by limiting the amount of toxic product formed or volatilized
A particulate matters
refers just to the suspended solid or liquid matter.
NIOSH has developed an analytical method meant to
sample for total elemental carbon as a simple indicate for DPM.
Classic chronic lung toxins that can cause pneumoconiosis
silica, coal dust, and asbestos.
Particles larger than about 100 μm
simply fall to the ground quickly
Deposition by diffusion
slow movement of small particles favors
Cold nitrogen gas is heavier than air
so the risk is greatest near the ground.
Chemical Composition
sometimes the primary driver for the toxicity of a material
Particles smaller than about 0.001 μm
start to act like gases, rather than like particles.
Diffusion
submicron particles
PM can indirectly cause
systemic toxicity by triggering inflammation in the lungs.
Airborne radon
tends to accumulate where uranium is stored or inside poorly ventilated basements or in certain geographical locations such as mines
The use of compressed gas cylinders has inherent dangers in their handling if the cylinder were to fall over and the valve snap off
the cylinder can become a projectile.
Air Sampling occupational exposure purposes
the eight hour time weighted average is the most commonly measured value
One concern about the cryogenic liquids is
the frost bite from extreme cold.
For a mixture of two or more flammable gases with LFL of ≤ 10% for each gas
the gas that has the smallest (LFL) will be the one that poses the most flammability hazard.
The higher the vapor pressure
the higher the concentration of the chemical at equilibrium.
The higher the temperature
the higher the vapor pressure.
High readings could lead to
the implementation of unnecessary control measures
Typically, samplers are set up around
the perimeter of an isolate asbestos dust containment area as a means of verifying the adequacy of the controls. These samples are typically taken using aggressive techniques, traditionally using a leaf blower and fans to stir up any settled or residual dust and make it accessible to air filter.
For more of a substance to evaporate (i.e., for the substance to boil)
the temperature must increase.
After radon turns to Radioactive polonium
then through several other radioactive isotopes including two forms of radioactive lead, and finally to lead-206. These intermediate radioactive materials are charged particulate matter and rapidly attach themselves to oppositely charged particles in the air.
As the nitrogen evaporates
there is a risk of violent oxidation of organic matter.
Because asbestos fibers can travel on air currents through the lung lengthwise, like an arrow
they can penetrate much deeper into the lung than a non fibrous particle, As a result, asbestos fibers can make it to the alveolar region of the lungs.
For the same liquid if different boiling point
this depends on the pressure of the atmosphere.
For asbestos control, the best method is
thoroughly wet the surface before removal or renovation
DPM significant contributor
to community cardiovascular morbidity and mortality in communities.
Some compounds react spontaneously in moist air (before inhaling them)
to form compounds that cause irritation to the respiratory system.
Surface sampling is used
to sample for large particles because they settle on the surfaces and do not suspend in the breathing zone.
Decomposition of organic material may produce
toxic (e.g., hydrogen sulfide) atmospheres & flammable (e.g., methane) atmospheres.
Once Asbesto fibers deposited in this region of the lungs, it is believed that the fibers
trigger an ineffective immune response by resident macrophages, which not only fails to remove the relatively insoluble fiber, but kills the macrophages in the process. This sets off a chain of immunological events, which results in scarring of the lungs and development of lung cancer.
Development of pneumoconiosis
typically requires years of exposure.
Soluble PM will be absorbed in
upper respiratory tract system.
General are sampling is also
used for sampling airborne bacterial and fungal spores.
Lower flammability limit (LFL)
usually expressed in volume per cent
Another concern is that if the cryogenic liquid spills, the spill
vaporizes rapidly, producing gas that is denser than the air which causes oxygen deficiency especially in a closed area
Electrostatic precipitation
when particles are charged
PM may also enter the lymphatic system
where they can dissolve or remain.
Any concentration above the UFL
will create an enriched mixture with the atmospheric oxygen. The atmospheric oxygen in this mixture is not sufficient to form an ignitable mixture.
Seven samples are enough for a working area
with 8 to 10 employees,
Flammable liquids
with a flash point < 100 F
Vapor pressures of liquids at ambient temperatures increase
with decreasing boiling points. If the boiling point is low - then we need shorter time to release the vapor
Eight samples are enough for a working are
with eleven employees or more.
Generally, Particles must be
≤ 2 μm to penetrate to the inner recesses of the lungs (less than/equal to)
Generally, particles must be
≤ 2 μm to penetrate to the inner recesses of the lungs.