(IAQ)

Introduction  Inorganic gaseous pollutants are the major contributors to Indoor quality problems  Combustion appliances and tobacco smoke are the major sources of gases along with other types of pollutants  These Inorganic gaseous pollutants include  Carbon monoxide.  Sulfur dioxide.  Nitrous oxide.  Nitrogen dioxide.

Factors effecting concentration.  The emission patterns and concentrations of the pollutants depend on Following factors:  Types of Fuels used  Combustion efficiency  Appliance design  Ventilation system  Operating conditions  Maintenance  Frequency of use

Appliances based on Fuel type and their application  Un-vented space heaters  Wood burning stoves  Furnaces  Fire places

Behavior of combustion appliances  Un-vented space heaters  In this type of device the pollutant concentration is maximum within the first hour of furnace operation  The concentrations come to a standard steady state as the device is shut down  Wood burning appliances  These appliances emit pollutants intermittently and depend completely on the type of wood used  The other pollutants released due to the devices of this type include organic compounds (like HCHO)  The indoor to outdoor ratio of these Inorganic gaseous pollutants can be well over unity

Average NO 2, NO, and CO Concentrations in a house

Health Effects of CO 2  The ratio of indoor to outdoor concentration of CO 2 is generally greater than ‘1’  The concentration level of CO 2 to cause any serious health problems in the range of 30,000 ppm  Respiration is effected at concentration levels from and above 15,000 ppm  Above 30,000 ppm it can cause headaches, dizziness and nausea  Prolonged exposure to concentration above 5000 ppm can increase the incidence of illness  The concentration of 5000 ppm is adopted as TLV for the submarines

Health Effects of CO  Health effects due to CO include loss of alertness, impaired perception, learning disorders, sleep deprivation, drowsiness and confusion  Health effects due to prolonged exposure to low concentration have been controversial, but acute illness and deaths have been reported  CO combines with hemoglobin and myoglobin to stop the supply of oxygen to tissues affecting brain, myocardium and muscle tissues  Carboxyhemoglobin can cause severe health effects at various percentage levels in blood  Loss of vigilance 3% - 5%  Loss of hand to eye - 10%

Health Effects of NO and NO 2  At high level there can be very serious health effects like coma and eventual death  NO and NO 2 are the most reactive species of the nitrogen oxides  They combine with other indoor pollutants to form complex toxic substances  React with amines like benzo(a)pyrene and pyrelene to form carcinogenic nitrosoamine and mutagens

Health Effects of SO 2 and Cl 2  SO 2, another pollutant found indoor at 0.25 – 0.5 ppm can cause bronchioconstriction in exercising asthmatics  Short-term exposure to the low level of SO 2 can cause irritation  Long term exposure can cause functional changes in lung making the body susceptible to damage by other pollutants  Cl 2 gas another gas found when two cleaning agents are mixed together one containing acidic compound and another sodium hypochlorite  Cl 2 gas can cause coughing, breathlessness, irritation of upper airways, bronco spasms, nauseas and vomiting

Sources Unvented space heaters  The unvented gas heater is one of the major sources of pollutants like Inorganic gaseous pollutants  This device can be classified into two categories  Gas space heaters – heaters of this type use gas as fuel  Kerosene space heaters - heaters that use kerosene as fuel

Classification of Kerosene space heaters  Convective  Radiant  Convective / Radiant  Two stage  Wickless

Factors affecting Emission rates  Emission rates of pollutants from kerosene space heaters depends on the following factors  Usage pattern  Type of heater  Type of fuel  Age of heater

Significant emissions from Kerosene space heaters  All heaters emit NO, NO 2, CO, CO 2, respirable particles and formaldehyde  Emission rate of CO 2 depends on type of fuel used and duration of burning  The average CO 2 emissions rates are:  49,8000 +/ mg/Kg from natural gas heaters  60,500 +/ mg/Kg from a propane heater  70,000 mg/Kg from a kerosene heater  CO, NO, NO 2 and formaldehyde were emitted in various conditions in majority of the experiments

Emission Rates from Vented and Unvented Gas-fired Room Heaters Operating Conditions Concentration NO (mg / h) NO 2 (mg / h) CO (mg / h) HCHO (mg / h) Ventedaverage range317 – 4578< 3 – – – 300 Unventedaverage range183 – – –

Wood burning stove’s fireplaces and Furnaces as sources  These are potential sources for both indoor and outdoor air  They emit NO, NO 2, CO, CO 2, SO 2, respirable suspended particles, benzo(a)pyrene and formaldehyde (which are vented outside)  Cracks and leaks in stovepipes, downdrafts, log roll over in fireplaces and negative air pressure cause the indoor pollution  The emissions of pollutants per cord of wood are generally:  0.5 – 1.5 lb of sulphur  0.7 – 2.6 lb of NO x  300 – 1200 lb of CO

Gas stoves and Ovens  Gas stoves produce pollutants like CO, CO 2, NO, NO 2 and aldehyde indoors  CO level is increased by 20 – 25 ppm within the first 30 mins of operation, 1.2 ppm of NO in first 45 mins and 25 ppm of NO 2  CO 2 emissions for ovens in steady state were higher for a new stove compared to an old stove  The concentration of indoor pollutant is decided by  Air changes per hour  Number of heaters  Frequency of use  Airspace volume

Emissions from Gas Stoves

Other Combustion sources  Other sources of pollutants are water heaters, washers, dryers and attached garages  Several hobbies like welding and soldering etc are also sources of indoor air pollution  Tobacco smoke is the major contributor of respirable particles  Gas water heaters lead to high indoor concentration of Nitrogen oxides

Measuring Devices  Personal monitors are available only for CO, NO 2 and SO 2 and can work in all models  The most commonly used monitors are:  CODE – I  CODE – II  Portable / Stationary instruments are used to measure inorganic compounds concentration  Most common method used to measure CO and CO 2 is nondispersive infrared (NDIR) photometry

Other Measuring Devices  Individual concentration of gas in a gaseous mixture is measured by Thermal conductivity Detector (TCD)  Thermal conductivity Detector is used for quantifying CO, CO 2 and H 2 O  Flame photometric method is used for SO 2 and H 2 S

Effective Measuring Methods  The Gas filter Correlation method (GFC) is used to measure CO concentration (certified by EPA)  Ozone is measured by chemiluminescent method  SO 2 concentration is measured by:  Colorimetric method  Flame photometric detection (FPD)

Reagents for Colorimetric Determination of Selected Inorganic Gases CompoundReagentRange (ppm) AmmoniaModified Berthelot0 – 5 ChlorineDPD procedure0 – 5 Ethylene oxidePeriodate / PRA0 – 25 HydrazineP – DMAB0 – 20 Hydrochloric acidThixyanate method0 – 100 Hydrogen cyanideChloramine T / Pyr – Bard0 – 1 Hydrogen sulfideMethylene blue0 - 10

Source control  The major contributors are the wood burning stoves, so removal of them indoors substantially reduces the pollution  Replacement of wood burning stoves by oil or gas fired furnaces  Modification in the design of the gas and kerosene stoves is another way to subside the indoor pollution  Other preventive measures like proper operation and regular maintenance of the burner could be a possible alternative

Increased ventilation  Local and Mechanical ventilation are most effective in removing the pollutants  Hood installed over the cooking place is one of the most common local ventilation methods  Ductless Cooking ranges with Carbon filters are being used  Carbon filters have poor adsorption capacity (which can be improved by careful design)  Mechanical ventilation increases the air exchange rate hence decreasing the concentration of the pollutants

Air Cleaning  Absorption methods  This method can effectively remove the pollutants indoors  Liquid desiccant based air conditioning systems are being used indoors  Absorber using monoethanolamine is being used in submarines to reduce the concentration of CO 2  The systems failed when the outdoor concentration was much higher

Air Cleaning Adsorption methods  Commonly used adsorbents are:  Silica gel  Activated alumina  Activated carbon  Manganese oxides  These adsorbents should be able to remove the moisture from indoor air using solid adsorbents (desiccants)