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Respirable Particles. (IAQ). Introduction. A collective group of fine solid particles, aerosols, mist, smoke, dust, fibers and fumes are called Respirable particles Particles in the size range of less than 10  m remain in air for a longer time and are of particular interest

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Respirable Particles


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  • A collective group of fine solid particles, aerosols, mist, smoke, dust, fibers and fumes are called Respirable particles

  • Particles in the size range of less than 10m remain in air for a longer time and are of particular interest

  • These particulates are hazardous to human health:

    • They can penetrate into the Respiratory system

    • Can become carriers to toxic substances

  • Particulates that are smaller than 5m can enter into the lungs

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  • Particulates less than 0.5m can carry harmful toxin pollutants like radon, alpha particles and chemicals

  • The particulate size influences the sedimentation, impaction and diffusion of the particulate matter

  • Due to Impaction property, the particulate settle at the bends (for particles less than 0.5m) of respiratory tract

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Factors effecting deposition of the particulates in the respiratory tract

  • Size of the particulate

  • Density of the particulate

  • Shape of the particulate

  • Breathing pattern

  • Mean volumetric flow rate

  • Morphology of the respiratory tract

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Health Effects and Standards respiratory tract

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Health Effects respiratory tract

  • Many studies revealed that ETS has adverse health effects, which was backed even by the tobacco industry (1989 symposium)

  • Smoking is the major cause of lung cancer both in men and women

  • ETS smoke consisting of side-stream smoke (SS) and exhaled mainstream smoke (MS) is a major component of Indoor air pollutants

  • Fibers with different chemical compositions can induce tumors

  • Asbestos and other manmade fibers are carcinogenic

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Health standards of Fibers respiratory tract

  • Asbestos can also lead to lung cancer

  • Fibers with diameter less than 1m and length greater than 5-10 m are particularly dangerous

  • Ambient air quality standard for outdoor air is 75 mg/m³ for long-term exposure and 260 mg/m³ for short-term exposure on 24hr average

  • For particulate less than diameter of 10m the standards are:

    • 55 mg/m³ for long-term periods

    • 150 mg/m³ for short-term periods

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Sources respiratory tract

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Sources of Respirable Particles respiratory tract

  • The major sources of respirable particles are from outdoors, tobacco smoke, wood burning and other sources

  • Unfiltered air carrying pollutants from industries, power plants and automobile exhausts

  • Humans are major contributors of the indoor pollutants

  • Relatively highly populated house has numerous pollutants

  • Cigars, cigarettes and pipes are major sources of ETS

  • The ETS contains nicotine, respirable particles, poly cyclic aromatics, CO, acrolein, NOx and number of other chemicals

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Asbestos (a generic term) varieties respiratory tract

  • Actinolite

  • Amosite

  • Anthophyllite

  • Crocidolite

  • Tremolite

  • Chrysotile or white asbestos (accounts for 90% of fibers found)

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Analysis of Fibers and its sources respiratory tract

  • Analysis of fibers is usually by:

    • Scanning electron method (SEM)

    • Transmission electron method (TEM)

  • Indoor concentration is high at peak activities like high foot traffic

  • Sources of indoor fibers in air include carpets, curtains and insulation

  • Fibers of size between 5 – 200 m are particularly of great interest due to their toxicity

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Sources of Respirable Particles respiratory tract

  • Other sources of respirable particles are:

    • Gas fired appliances

    • Automotive airbags

    • Dust from laser printers

    • Industrial processes

    • Laser cutting of steel and welding are the major sources of particulates

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Sampling and Measurement respiratory tract

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Respirables Particle characteristics and samplers respiratory tract

  • The aerosol particles are measured by mean of an aerosol sampler

  • The filters are based on the following characteristics:

    • Collection efficiency

    • Pressure drop through filter

    • Background contamination

    • Compatibility to analytical methods

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Respirable Particles and measuring methods respiratory tract

  • Size of the particulate also helps in the selection of suitable removal equipment

  • ETS smoke is measured using are samplers and personal monitors

  • Fibrous particles can be detected by the intensity of scattered He – Ne laser light for particles

    • with length 2 – 200 m

    • Concentration of and above 0.0001 – 30 fibers/ cm³

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Control Strategies respiratory tract

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Mechanical Ventilation respiratory tract

  • This type of ventilation is divided to two types:

    • Fabric / cake filtration

    • Fibrous filtration

  • Cake filtration is used for high particulate concentration and large volume of gas

  • Fibrous filters are used for low particulate concentration and low flow rates

  • Extended surface area filters are more efficient than the panel filters for particles of micron ranges

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Panel filters respiratory tract

  • Panel filters are most frequently used mechanical filters for removing particles from air

  • Filters are classified according to the removal efficiencies as:

    • Low efficiency filters – metal filters

    • Polyester and glass pads have efficiency of 10%

    • Medium efficiency filters – (20 – 50) %

    • High efficiency filters - commonly used in hospitals, office buildings and highly protected indoors

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Mechanical filters and Electronic Air Cleaning respiratory tract

  • Other types include

    • High efficiency particle air (HEPA) have efficiency (99.99% - 99.9999%)

    • Ultra low particulate / penetration air (ULPA)

  • Using electrostatic technologies can increase efficiency of the filters

  • Electrostatic precipitator is the most efficient and widely used, as it removes up to 99% for particles less than 1m in size

  • Fine particles like ETS smoke can be removed by using both electrostatic field and ion generator together

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Absorption respiratory tract

  • Absorption devices

    • Wet collectors

    • Spray towers

    • Cyclone scrubbers

    • Impingement scrubbers

    • Venturi scrubbers

    • Sieve plate towers (successful in removing particles from effluent gases)

  • Liquid desiccants such as lithium chloride and triethylene glycol are commonly used for dehumidification

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Adsorption respiratory tract

  • Adsorption

    • Activated carbon

    • Impregnated alumina bed with electronic air cleaners (for tobacco smoke)