Respirable Particles

1. Respirable Particles (IAQ)

2. 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

3. 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

4. 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

5. Health Effects and Standards

6. 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

7. 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

8. Sources

9. 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

10. Asbestos (a generic term) varieties • Actinolite • Amosite • Anthophyllite • Crocidolite • Tremolite • Chrysotile or white asbestos (accounts for 90% of fibers found)

11. 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

12. 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

13. Sampling and Measurement

14. 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

15. 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

16. Characteristics of Direct-reading Particle Monitors

17. Control Strategies

18. 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

19. 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

20. 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

21. 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

22. Adsorption • Adsorption • Activated carbon • Impregnated alumina bed with electronic air cleaners (for tobacco smoke)