(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  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

Introduction

 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

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

Health Effects

 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

Health standards of Fibers

 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

Sources of Respirable Particles

 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

Asbestos (a generic term) varieties

 Actinolite  Amosite  Anthophyllite  Crocidolite  Tremolite  Chrysotile or white asbestos (accounts for 90% of fibers found)

Analysis of Fibers and its sources

 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

Sources of Respirable Particles

 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

Respirables Particle characteristics and samplers

 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

Respirable Particles and measuring methods

 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

Characteristics of Direct-reading Particle Monitors

Instrume nt Analytical Me thod

Aerosol photometer Light scattered at a Integrating nephelometer

Effe ctive Particle Type of Me asure me nt Size Range (micro me te r) Portable

Indirect measure of < 1.0 - 10.0

Yes fixed angle aerosol mass or dust Light scattered integrated Visual range; indirect over a wide angle (8 - 170 degrees) measure of respirable particles 0.1 - 1.0

No Yes Light Scattering optical counters Active scattering Light scattered at a fixed angle Light scattered of output Particle number distribution Particle number aerosol spectrometer of a He - Ne laser at a fixed angel distribution Condensation nuclei Condensation of nuclei counter Condensation nuclei by adiabatic expansion concentration 0.3 - 10.0 in upto 10 size ranges 0.08 - 4.5 in upto 48 size ranges 0.0025 - 1.0

No Yes Electrical aerosol analyser Respirable dust mass monitor Aerosol mass monitor and optical detection Electrostatic particle mobility analyzer Beta - attenuation Piezoelectric crystal Particle number distribution Cylone followed by an indirect measure of mass Particle mass concentration 0.0032 - 1 in 10 ranges < 10 0.01 - 10.0 No Yes Yes

Mechanical Ventilation

 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

Panel filters

 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

Mechanical filters and Electronic Air Cleaning

 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

Absorption



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

Adsorption



Adsorption

 Activated carbon  Impregnated alumina bed with electronic air cleaners (for tobacco smoke)