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VOLATILE ORGANIC COMPOUNDS

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  1. VOLATILE ORGANIC COMPOUNDS (IAQ)

  2. Introduction • A chemical having at least one carbon and hydrogen atom in its molecular structure is referred to as Organic Compound • Organic compounds are divided mainly based on their vapor pressure at room temperature into: • Volatile Organic Compounds (VP > 1 mm of Hg) • Semi-Volatile Organic Compounds(10E - 7 > VP < 1 mm of Hg) • Non-Volatile Organic Compounds (VP < 10 E -7 mm of Hg)

  3. Introduction(contd.…) • EPA conducted comprehensive studies on Indoor Air Quality in U.S. under the name of Total Exposure Assessment Methodology (TEAM) • The study showed that the targeted 22 chemicals (Pollutants) had higher concentrations indoors than outdoors • Formaldehyde (used in resin) is suspected of being carcinogenic at present indoor levels which may be a critical problem

  4. The 22 Targeted VOCs by the U.S. EPA (1986)

  5. Pollutants associated with various activity levels

  6. Pollutants associated with various activity levels • Source: Sterling et al., 1990.

  7. Health Effects and Standards

  8. Health effects due to exposure to VOCs • Health effects due to exposure to VOCs at typical Industrial Environments are derived from animal studies which can be related to humans • Little is known about the chronic effects of a mixture of VOCs (particularly at low concentrations) • Indoor Environments (residences in particular) have different types of exposure to the pollutant: • High Concentration but for a short period • Low concentration but for a longer period • In short-term exposure individuals are exposed to one or a mixture of compounds depending on their activity levels

  9. Health effects due to exposure to contaminants depends on: • Exposure time • Pollutant types • Health status of the individual at the time of exposure • Pollutant concentration (an important factor)

  10. Health effects due to Aldehyde Exposure Formaldehyde • Formaldehyde is colorless but has distinct pungent odor that makes it detectable (even at concentrations as low as 0.05ppm) • Formaldehyde concentration is higher in mobile homes and houses with Urea Formaldehyde Foam Insulation (UFFI) • Formaldehyde has both acute and chronic health effects like: Irritation of eyes, upper airway, etc

  11. Health effects due to formaldehyde exposure at various concentrations • Source: NAS, 1981.

  12. Studies on formaldehyde exposure 1396 residents of UFFI homes and 1395 of non-UFFI homes (Thun et al.,1984) Not reported Wheezing: e, 60%; ne, 10%; Burning skin: e, 70%; ne, 10%; 70 employees in 7 mobile homes and 34 non-exposed employees in 3 buildings Mobile home: 0.24 – 0.55 ppm Building: 0.05 – 0.11 ppm Menstrual irregularities: e, 35%; ne, none Eye irritation: e, 55%, ne,15%; Headache: e,80%; ne, 22%; 21 workers in mobile homes and 18 workers in buildings Mobile home: 0.12 – 0.16 ppm Building: not reported Eye irritation: e, 81%; ne, 17%; Throat irritation: e, 57%; ne, 22%; Fatigue: e,81%; ne, 22%; Headache: e, 76%; ne, 11%; Where: e – Exposed and ne – Non-exposed.

  13. Health Effects due to Exposure to Formaldehyde and Ethers • Formaldehyde at high concentration can cause buccal cavity cancer and nasopharyngeal cancer in human beings • Low concentrations can also be fatal or can cause serious threat to health and the risk of developing cancer is: • 1 in 10,000 Exposed for 10 yrs at 0.07 ppm • 1 in 5,000 if exposed at 0.1 ppm • The Ethers cause anesthetic effect in humans, which leads to pulmonary edema, vomiting, headache and nausea

  14. Health effects due to Exposure to high concentration of ketones • Narcosis • Nausea • Headache • Dizziness • Irritation of mucous membrane • Loss of co-ordination

  15. Effects of Formaldehyde exposure on human health

  16. Health effects due to exposure to Aliphatic and Aromatic Hydrocarbons • Propane and more complex hydrocarbons depress the central nervous system and cause mild irritation of the mucous membrane • Cyclic Hydrocarbons have same effect as the aliphatic hydrocarbons • Aromatic Hydrocarbons cause: • irritation of mucous membrane, eyes and respiratory system • pulmonary edema • pneumonitis • Benzene, a hydrocarbon, is a human carcinogen

  17. Health effects due to exposure to Chlorinated Hydrocarbons • High volatility of the chlorinated hydrocarbons leads to substantial exposure through inhalation • Chlorinated hydrocarbons cause • Irritation to eyes • Irritation to skin • Irritation to respiratory system • Severe functional • Severe damage to the liver and kidneys

  18. Changing exposure limits of Chlorinated Hydrocarbons • Source: Henschler, 1990.

  19. Health effects due to exposure to Alcohols • Compounds like phenol and cresol cause • Difficulty in swallowing • Diarrhea • Tremors • Convulsions • Ingestion of Methanol causes damage to the optical nerve leading to blindness

  20. Mixture of VOCs • Chemicals are found in a room generally in a mixture form • Synergistic interactions of pollutants leads to different chemical compounds • Any building related health effects due to indoor pollutants is referred to as Sick Building Syndrome (SBS) or Tight Building syndrome (TBS)

  21. Exposure Limits • Threshold limit Value (TLV) is the level of a chemical that ACGIH deems safe for a worker to be exposed to day after day • OSHA, ASHRAE recommended one-tenth of TLV as maximum allowed indoor concentration • Based on several studies American Industrial Hygiene Association (AIHA) adopted 5 mg / m³ as a guideline for VOCs • ASHRAE (62-1999) suggests the following air exchange rate’s : -- Residential Facilities: minimum of 15 ft³ /person/ min -- Commercial and Institutional facilities: 15 to 60 cf/person/min

  22. Sources and Indoor Concentrations

  23. Formaldehyde • Formaldehyde, a major VOC, is released mainly from materials that contain UFFA, a type of resin. These materials can include: • Building materials • Home/Office Furnishings • medium density fiberboard • particle board • carpet • electrical switches • Formaldehyde is used in resins because of its following properties • Excellent bonding properties • Inexpensive

  24. Formaldehyde uses and potential indoor sources

  25. Formaldehyde emission rates of several building materials

  26. Formaldehyde • The concentration of HCHO fluctuates with • Seasonal variation of temperature • Relative humidity, and • Moisture content of several materials • HCHO is produced during the various processes such as • Operation of combustion appliances (gas or kerosene stove, fireplace etc.) • Smoking

  27. Formaldehyde concentration in homes resulting from combustion appliances • Source: Hawthorne and Matthews, 1985

  28. Sources of VOCs • VOCs other than Formaldehyde are released from several other products such as • Combustion products • VOCs emitted as a result of incomplete combustion of fuel release chemicals like methane, ethane, propane and hexane • Wood also releases Polynuclear Aromatic Hydrocarbons (PAH) • Tobacco smoke (depending on the number of cigarettes smoked)

  29. Emission (in ppm) Emissions of Organic Chemicals from Household Products Compound Adhesives Coatings Fabrics Foam Lubricants 1,2-Dichloroethane 0.8 0.75 Benzene 0.9 0.6 0.7 0.2 Carbon tetrachloride 1.00 0.18 Chloroform 0.15 0.10 0.04 0.20 Ethyl benzene Limonene Methyl chloroform 0.4 0.2 0.07 1.00 0.50 Styrene 0.17 5.20 0.02 12.54 Tetrachloroethylene 0.60 0.30 65.0 0.10 Trichloroethylene 0.30 0.09 0.03 0.10 0.10

  30. Emission in ppm Compound Paints Rubber Tape Cosmetics deodorants Emission of Organic Chemicals from Household Products 1,2-Dichloroethane 3.25 Benzene 0.90 0.10 0.69 Carbon tetrachloride 4.20 0.75 Chloroform 0.90 0.05 Ethyl benzene 527.80 0.20 Limonene 0.40 Methyl chloroform 0.10 0.10 0.20 Styrene 33.50 0.15 0.10 1.10 0.15 Tetrachloroethylene 0.20 0.08 0.70 Trichloroethylene 0.07 0.09 1.90

  31. Emission (in ppm) Emission of Organic Chemicals from Household Products Compound Health & beauty aids Electrical equipment Misc. house wares Ink pens 1,2-Dichloroethane 0.06 Benzene 1.85 0.02 1.10 0.40 Carbon tetrachloride 0.00 0.04 0.20 Chloroform 0.23 4.85 10.00 Ethyl benzene 0.80 Limonene 1.00 1.80 Methyl chloroform 0.01 0.03 0.19 0.10 Styrene 0.17 0.05 0.02 0.30 Tetrachloroethylene 0.05 2.00 Trichloroethylene 0.11 0.01 0.06 0.07

  32. Emission of Organic Chemicals from Household Products Source: Ozkaynak et al., 1987.

  33. Sources of VOCs Carpets and paints • Carpets and paints are large contributors and cover nearly 95% of room surface area • VOCs are emitted by the use of oil-based paints • Carpets emit VOCs at first but gradually VOC emission rates diminish • Newly carpeted room should be properly ventilated  for several days after installation, or carpets can be pre-ventilated in a humidity controlled warehouse

  34. Sources of VOCs Water • During treatment of water before supply under go several processes. • Common by-products of this treated water are: • Chloroform • Carbon tetrachloride, and • 1,2,3-trichloropropane Human beings • Acetone :1200 * 10 E (-6) / m³ • Ethanol :240 mg/m³

  35. Emission rates of organics by humans

  36. Sampling And Measurement

  37. Most commonly used analytical type air quality monitoring equipment Personal monitors • Lightweight monitors convenient to carry and to handle Portable monitors • These can moved during sampling Stationary monitors • These can operated only from a fixed place

  38. Principles followed by collectors during data collection • Air Displacement • Condensation • Air is passed through a U-tube followed by subsequent cooling of the sample •  Gas washing or Absorption • The contaminated air or the sample is passed (bubbled) through a liquid, where it may dissolve or react with the liquid • Distilled water is used for readily soluble gases

  39. Principles followed by collectors during data collection Adsorption:Frequently used Solid adsorption media are • Activated carbon • Silica gel • Sieves • Tenax-GC, Tenax-TA • XAD-2, XAD-4 • Chromosorb 101, 102 and 103 etc.

  40. Principles followed by collectors during data collection Adsorption • The key factors for successful use of these adsorbents are: • Cleaning of the sorbent tube to remove background contamination by • Heating to high temperatures in vacuum • Flowing small quantity of inert gas • Accurate determination of the sampling rate

  41. Analytical methods used • Colorimetric and spectrometric methods are used to quantify a pollutant • Colorimetric method is commonly used for measurement of Formaldehyde • A method referred to as Acid bleached pararosaniline method: • Equivalent to the chromo tropic acid method • Twice as sensitive

  42. Most commonly used detectors for analysis Thermal conductivity detector (TCD) • Suitable inorganic gases as it measures changes in thermal conductivity Hot wire detector (HWD) • Measures thermal conductivity and is also suitable for inorganic gases Flame Ionization Detector (FID) • Detects difference in flame ionization due to combustion suitable for: • Aliphatic compounds • Aromatic compounds

  43. Most commonly used detectors for analysis Electron Capture Detector (ECD) • Measures the current flow between the electrodes and is suitable for chlorinated hydrocarbons Flame Photometric Detector (FPD) • Measures light from excited state of Sulphur and Phosphorous compounds in hydrogen flame Mass Selective Detector (MSD) • It is suitable for most indoor pollutants • This method provides quantitative analysis, and • Identifies different chemicals in a mixture

  44. Control Strategies

  45. Source control • Selection of the products that emit very less VOCs • Concentration due to selected building materials should be below 0.05 ppm • Substitution of the material with a material of similar properties having low emission rates • Avoiding the materials containing formaldehyde (like UFFI, Ammonium Sulphite)

  46. Suggested Emission rates of products in building

  47. Ventilation Types of ventilation • Infiltration of outdoor air • One of the common cost effective methods • Ineffective if outside air or the in filtered air is itself polluted • Natural ventilation • This happens when all the doors and windows are properly opened • This is the most effective method as there is constant air inflow • The only disadvantage is the increase in the heating or cooling costs

  48. Ventilation • Mechanical ventilation • Use of HVAC system (normally suitable for non-residential places) • Advantageous over other types of ventilation • Energy for heating or cooling can be recovered from the exhaust air • Local Ventilation • This method produces a low pressure around the source using a blower fan • This method is a disadvantage if the source is of continuous type

  49. Air Cleaning Removal by Catalytic Converters • Pollutants found in the air can be converted to less harmful gas using the catalytic converters • Some catalysts used to remove Formaldehyde are: • Purafil • Activated carbon • Alumina oxide • Ammonia fumigation is the method employed for formaldehyde removal (particularly for mobile homes)

  50. Air Cleaning Removal by absorption • Used for organic pollutant removal from indoor air • Experiments showed removal of formaldehyde up to 63% (but were not tested practically) Removal by adsorption • Gases are attracted on to the solid and they remain until reversed by applying vacuum or heat • Efficiency of adsorbant should be known before using a activated solid material for a particular pollutant