Strictly as per the compliance and regulations of:

he Environmental Protection Agency (EPA) of USA lists indoor air quality among the top 5 risks to human health, probably because indoor air can be 2-5 times more polluted than outdoor air. While homeowners can't see the majority of indoor air contaminants, every cubic foot of air breathed carries a mixture of millions of microscopic particles such as pollen, mold spores and dust mite debris. In small concentrations, these particles and gasses may cause discomfort in the home. In significant concentrations, they can cause sickness as these are among the most troublesome triggers of such ailments as asthma and allergies.

Particulate matter is the reason of particle pollution and it is a complex mixture of extremely small particles and liquid droplets suspended in a gas, which is usually air. Particulate pollution made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals and soil or dust particles. These particles can be suspended in the air for long periods of time. Some particles are large or dark enough to be seen as soot or smoke. Others are so small that individually they can only be detected with an electron microscope. Normally they are classified as coarse particles equal or greater than 10 µm and fine particles are less than 2.5 µm. Particulate matter is primarily formed from chemical reactions in the atmosphere and through fuel combustion with insufficient oxygen e.g. motor vehicles, power generation, industrial facilities, residential fire places, wood stoves and agricultural burning. Most people spend most of their time indoors. The most recent nationwide study of time budgets (Robinson and Nelson, 1995), based on interviews with 9.386 respondents in 1993-1994, indicates that US residents spend 87.2%of their time indoors, 7.25 in or near a vehicle and only 5.65 outdoors. This paper deals with field studies of particles indoors and outdoors, concentrating particularly on large-scale surveys of homes and buildings. The observed indoor particle concentrations are presented, together with the contributions of these studies toward understanding important parameters such as air exchange rates, source emission rates and penetration factors.

The manner in which particles are formed determines the size and composition of particles. The four main mechanisms of particulate matter formation described below.

? Physical attrition ? Combustion particle burnout.

? Homogeneous nucleation and heterogeneous nucleation of vapor phase compounds in hot gas streams. ? Release of solids during the evaporation of solids containing droplets in hot gas streams.

In this experiment, outdoor and indoor air qualities were measured. The experiments were carried out in four different locations in Rajshahi city to measure the outdoor air quality as well as in Higher Education Quality Enhancement Project (HEQEP) sub project CP-521 office room in Rajshahi University of Engineering and Technology (RUET), Rajshahi for indoor air quality. ? the total number of people is living into the location.

? the environmental condition around in location that affects the generation of particulate matter.

? the number of vehicles passing through or near the location and

? the number of industries and factories in or around the locations.

On the basis of above factors the following locations in the city were selected: The number of particulate matter (PM) per unit of volume of the room was measured in both using and not using air conditioner. The room had only one ceiling fan and no ventilator. For measuring the concentration of particulate matter, the following conditions were taken for office room: ? Closing all doors and windows with ceiling fan on. ? Closing all doors and windows with ceiling fan off.

? Opening all doors and windows with ceiling fan on. ? Opening all doors and windows with ceiling fan off. ? Fitting filters to windows with windows open.

The Optical Particle Counter (OPC) SOLAIR-3100 of Lighthouse, UK, was used to measure the particle size distribution in both outdoor and indoor air. The specification of the OPC is given in APPENDIX I and the photographic view of the OPC is shown in Fig. 1. The device was operated with battery. The sampling probes were connected to the terminal. By pressing the power switch the device was turned on. Measuring mood, particle size, data storage, data printing, sampling time, frequency, delay and holding times were set up. The particle size range was 0.3 to 25 micrometers. Then sampling time was selected as 30 seconds for measurement. After that the interval was selected. It ranges from 1 sec to 24 hrs. We selected the interval between each measurement was one minute. Count per cubic meter was selected as measuring unit. Then the "OK" key was pressed to conform the setting and then pressed "SET" key to shift the measurement screen. After taking each data the machine was switched off. Once the measurement was finished, the data was dumped from the device. After getting all the data we made the device set at OFF.

Figs. 2 to 5 show the particle size distribution in different locations of Rajshahi city for outdoor air quality. From the figures it is clear that Maximum PM was found at Alupotti crossing and then the particle concentration decreases gradually in RDA market (2 nd floor), Bus Terminal and Kumarpara. The total number of people staying in Alupotti crossing was maximum compared to the other locations. The number of vehicles, density of the shops and number of industries and factories around that location was also greater compared to RDA market, bus terminal and Kumarpara which made the difference of particle concentration of that locations. The indoor air quality in HEQEP sub project CP-521 office room has been shown in Figs. 6 to 8. The figures show that the particle concentration was higher in non air conditioning room than air conditioning room. The particle concentration was also varied due to opening and closing the doors and windows with the ceiling fan on and off. The particulate matter was maximum when all the doors and windows were open and the ceiling fan was off. The particulate matter was reduced by fitting filters into the windows.

From the experimental investigations, the following conclusions may be drawn:

? Out of the places in which data were taken, outdoor air quality is the dirtiest in Allupatti crossing in Rajshahi city

? Cleanest indoor air can be achieved by fitting submicron filters in doors and windows of the room.

V.