A SURVEY OF INDOOR AIR QUALITY PROBLEMS IN AIR-CONDITIONED BUILDINGS IN INDIA

Transcription

1 A SURVEY OF INDOOR AIR QUALITY PROBLEMS IN AIR-CONDITIONED BUILDINGS IN INDIA S Kalaiselvam 1, * JR Robin 1, S Jose 2,S Iniyan 1, AA Samuel 3 1 Department of Mechanical Engineering, Anna University, Chennai , India 2 Department of Mechanical Engineering, St. Joseph s College of Engineering, Chennai , India 3 College of Engineering, Vellore Institute of Technology, Vellore , India ABSTRACT The indoor environment is intuitively considered a refuge, a safe place not only from inclement weather and temperature extremes but also from outdoor air pollutants. Over the years, buildings have been made more airtight to conserve energy. The scientific evidence has indicated that the air within homes and other buildings can be more severely polluted than the outdoor air in even the largest and most industrialized cities. Other research indicates that people spend approximately 90 percent of their time indoors. Thus, for many people, the risks to health may be greater due to exposure to air pollution indoors than outdoors. Maintaining a healthy and comfortable indoor environment in any building requires integrating many components of a complex system. A survey was conducted to study the air quality related factors and their influence in various types of offices. The parameters such as CO 2 content, air velocity, dust, odour and humidity were analyzed. This survey will helpful in detecting the presence or absence of health problems. It is noticed that among various building analyzed Restaurants, software companies and computer centres are found to be poorly ventilated. Odour seems to be a problem in majority of the buildings. INDEX TERMS Indoor Air Quality, Comfort. INTRODUCTION In India there has been considerable improvement in the living standard of the people due to rapid industrialization and urbanization. However, indiscriminate industrialization and urbanization have caused environmental pollution problems in certain areas of the country and specially air pollution problems are being experienced in major cities and near the industrial complexes. An Indoor air Quality survey is conducted in one of the fourth largest metropolis (Chennai) in India. This metropolitan area covers an extent of 1172 sq. km of which the corporation area, which is identified as the city extends over 172 sq. km. As per the census the population of City is 43 lakhs. A recent study found that the levels of suspended particular matter (SPM) present in the atmosphere ranged from 274 to 1,470 micrograms/cubic meter (mg/m 3 ) in several areas, which was much higher than the World Health Origination (WHO) prescribed limit of 200 mg/m 3. The level of carbon monoxide ranged from 12 to 70 parts per million (ppm) as against the permitted level of 35-ppm. These facts only indicate that the indoor air pollution will be much severe. It can cause a wide variety of negative health effects ranging from eye irritation, to heart and lung disease. It can also cause reduced productivity and large economic losses. Danish and Environmental Production Agencies (EPA) studies have analyzed "sick building syndrome", which links indoor pollutants to dizziness, headaches, coughing, sneezing, nausea, burning eyes, chronic fatigue, and flu-like symptoms. A healthy indoor environment is one in which the surroundings contribute to productivity, comfort, and a sense of health and well being. The indoor air should be free from significant levels of odour, dust and contaminants. Ventilation should be proper to prevent stuffiness without creating drafts. Good indoor air quality enhances occupant health, comfort, and workplace productivity. It is shown that indoor air quality has a noticeable effect on the intellectual efficiency and the health of the uses.(singh.j, 1996) In fact, recent estimates place the direct health care costs or poor IAQ in the U.S at $ 30 billion, with sick leave and productivity losses adding another almost $ 100 billion annually (Fisk W and A.Rosenfeld, 1997). William (2002) has reported that maintaining better working condition improved the worker performance by even a fraction of a percent or reduced sick leave by a day or more per year. This is significant hence every organization should have a status report on Indoor Air Quality as a tool for productivity improvement. INDOOR AIR QUALITY (IAQ) SURVEY * Corresponding author kalais_s@yahoo.com 893

2 A detailed survey was conducted in more than 300 buildings such as offices, shopping complexes, bank building, conference halls, theaters and industrial buildings. The objective was to collect first hand information for the occupants and also to measure the IAQ parameters for direct assessment. The information thus gathered were analyzed and the results projected. Room air temperature, air velocity, relative humidity and CO 2 concentration were measured at various locations for a period of 8 hrs in a day and recorded. Presence of Dust, moisture and odour were also assessed. The questionnaire is used to collect information on perceived comfort and complaints from the occupants. The concentration of carbon dioxide (CO 2 ) was measured to assess the adequacy of fresh air provision by the air-handling unit in meeting the occupancy load. Temperature and relative humidity (RH) measurements were made with a simple thermohygrometer. Accuracy levels of the instruments are ±0.1 C for temperature and ±1% RH for the RH measurements and all the measurements were made as per ASHRAE and ASHRAE 113. Air velocity within an air stream varies considerably. It is extremely difficult to measure air velocity at supply diffusers because of turbulence around the mixing vanes. The best estimate of air velocity is achieved by averaging the results of a number of measurements. This is done as per the ASTM Standard Practice D The concentration of carbon dioxide (CO2) is measured with a direct reading meter, which uses the infrared rays. The relative occupancy, air damper settings, and ambient conditions are noted at regular intervals. CO 2 measurements were taken in locations away from proximity of any sources that could directly influence the reading. The fresh air damper opening air infiltration, room sealing characteristics and power consumption was also noted for analysis. The levels of CO 2 in many offices were found to be appreciably below the threshold levels prescribed by ASHRAE. In same buildings fresh air mixing was the problem and in few others, it was infiltration. The frequency of door opening in many rooms also plays a prominent role. Sealing of doors was poor in many rooms leading to large leakage of air and poor return air velocities. This lead to increased power consumption and poor system efficiencies. As per the methodology given in ASHRAE 62. from the difference in the CO 2 levels inside and out side the room, the ventilation supplied per person was computed. Based on this, the ventilation in the room was distinguished to be of different characteristics. Above 41% of the investigated rooms were found to have deficient ventilation. 25% of the buildings were found to have moderate levels of ventilation, while the rest were fairly ventilated. These levels could be worse if the rooms were better sealed to avoid infiltration. Table 1. Indicates the summery of the ventilation status of various types of buildings. Table 1. Summary of the Ventilation Status Types of Building Poorly Ventilated (%) Moderately Ventilated (%) Well Ventilated (%) Total % Banks Computer Centres Conference Halls Departmental Stores Industries Laboratories Offices Others Restaurants Showrooms Software Companies Theatres Poorly Ventilated - Below 70 % of ASHRAE Standard Moderately Ventilated - Does not meet ASHRAE Standard but falls within 70% of it Well Ventilated - Meets or exceeds ASHRAE Standard

3 RESULTS AND DISCUSSION As indicated in Fig.1, nearly 58% of the rooms were found to be prone to greater sources of sick building syndrome, of which 4% were highly prominent, while remaining were moderate. This level of SBS was mainly due to the presence of higher levels of particulate matter, odor and dust accumulation in the rooms that were investigated. This is due to the improper ventilation that is provided, as the dilution of the pollutants/odor in the rooms are not possible Sick Building Syndrome Ventilation. 34% Moderat e 54% Present 4% Nil 42% Moderate Ventilation 25% Poor Ventilation 41% Figure 1. presentage of SBS in the room. Figure 2. Ventilation status based on CO 2 It was found that in 97% of the rooms, the occupied zone lacked room air movement as prescribed by ASHRAE. This results in the accumulation of higher levels of dead zones in the rooms leading to stagnation of pollutants. This is shown in fig.2. A study on the distribution of CO 2 in the room showed that PPM levels were fluctuating inside the room. Most of the designers do not consider to maintaining the room velocity so as to avoid poor IAQ conditions. There is a need for designing the room and the interiors for IAQ. Dead zones were found in many places, that was shown in fig. 3, this is a serious problem to be considered immediately. Velocity < SHRAE std. Velocity in Occupied Zone 97% Velocity > SHRAE std. 3% Rated Occupancy Percentage < 100 % 59% < 25 % occupancy 3% <75 % 30% < 50 % 8% Figure 3. velocity in Occupied Zone Figure 4. Occupancy percentage Many rooms were found to be poorly occupied compared to the designed levels of occupancy as shown in fig.4. This shows that the rooms were designed with a higher factor of safety leading to higher loss in the energy in many rooms. Nearly 59% of the building fall in this category. On part load operations, in addition to energy loss, there will be serious IAQ issue to he labeled. The use of Variable Air Volume (VAV) in many sites could save large amount of energy as well as help in maintaining higher IAQ. In most of the places it was found that the temperature varied from the 22 to 26 o C and it is accepted as per ASHRAE standard 55. The temperatures in the occupied zone are not uniformly distributed leading to discomfort for the occupants. It can be avoided by maintaining proper room air distribution in the occupied zone. Most of the heat transfer between supply and room air occurs above 1.8 m level. When properly selected, these outlets produce resultant velocities in the range of 0.15 m/s to 0.24 m/s through out the occupied zone (Kenneth, 1999). 895

4 Dust in Rooms Dust Present 56% No Dust 44% Figure 5. Dust presence in rooms Relative Humidity (RH) in the occupied zone of the various building ranged from 55% to 70%, confirming to standards for indoor thermal conditions. Even high levels of humidity do not affect human health. Marc E. Fountain (2000) found few differences in human response to humidity exposures between 60% RH and 90% RH. Known health effects related to high humidity are primarily caused by the growth and spread of biotic agents under elevated humilities, although humidity interactions with nonbiotic pollutants, such as formaldehyde, may also cause adverse effects.(anne, 2000) High humidity and moist materials provide ideal environments for the excessive growth of microorganisms. This may result in additional health concerns such as allergic reactions. Increased humidity in long-term can also foster the growth of dust mites. Dust mites are a major cause of allergic reactions and asthma. Hence steps should be taken not to allow the RH value to go beyond the standard. Particulate matter is the term given to the tiny particles of solid or semi-solid material found in the atmosphere. Particulate in size less 50 microns are called Total Suspended Particulate (TSP). Particles larger than that range tend to settle down. Particulate matter of 10 micrometers in diameter and smaller is considered inhalable. This particulate matter is commonly called PM10. Particles inhaled by humans are segregated by size during deposition within the respiratory system. The major regions of the respiratory system differ widely in structure, size, function, sensitivity, or reactivity to deposited particles and to the mechanism of particle elimination from the system. If the relative humidity in occupied spaces and low velocity dusts and plenums exceed 70%, fungal contamination can occur.(ashrae 62) Particle movement in a ventilated area is a complicated phenomenon and is influenced by many factors such as airflow pattern, geometrical configuration, particle properties, ventilation condition, supply and exhaust diffuser location, internal partitions, thermal buoyancy due to heat generated by occupants and equipment, etc.(weizhen Lu, 2001) Accumulation of dust in the rooms was a common feature in many rooms that were investigated. About 56% of the places that were investigated, had greater amount of dust accumulation. The accumulation of dust was due to the presence of the doormats inside the rooms. The presence of dust inside rooms is highlighted in fig. 5. Analysis of the results showed that 72% of the rooms that were investigated had doormats within the room. Hence it was concluded that the location of doormats was an important factor for the accumulation of dust in the buildings. It was also found that wearing footwear was permitted in 79 % of the buildings. Reports reveal that the particulate pollutants in many parts of city were closer to the threshold limit. Hence ventilation rate and location of doormats are to be fixed to avoid the presence of dust. Odor was one of the problems found to be existing in many places. It was found that 88% of the investigated rooms had odor problems. The sources of odor were explicit in many cases. It was mainly due to the people being permitted to wear shoes within the room. Apart from this, the presence of photocopiers, bookshelves, Newly Painted Articles were predominant sources of odor. The presence of odor is one of the major sources of Sick Building Syndrome. It was found that in 22% of the rooms, explicit evidence of the presence of other pollutant sources were present. These pollutants ranged from the emission of pollutants from the photocopiers and other out side pollutant sources. The presence of buildings closer to roadsides had greater sources of particulate matter. Processing sites were found to be a major source due to the chemicals used in process industries. It is noticed that in 46% of the places people experienced the stuffiness; this leads to poor working environment and cause discomfort. The stuffiness in the air-conditioned room is mainly due to the accumulation of pollutant in the occupied zone. ASHRAE acknowledge that the prescriptive standard provides an indirect solution to the control of contaminants. Ventilation is not a pollutant specific strategy (David T. Grimsrud, 1999), dilution of indoor air with clean outdoor air reduces concentrations of all airborne contaminants. Nearly 56% of the air 896

5 condition building are having air curtains, The primary purpose of the Climate Control Air Curtain is to prevent the influx of outside air through an opening in to heated or cooled area. It also prevents the influx of the dust particles or atmospheric vapor. CONCLUSION Sick Building Syndrome (SBS) is explicitly prevalent in many sites leading to lesser productivity. The sources of odor were predominant and can be avoided. Minimum ventilation rate must be delivered to each room to dilute the pollutant concentration. By providing proper ventilation as per requirement alone does not maintain Indoor air Quality (IAQ). Proper selection and positioning of the supply and return terminals provide better distribution in the occupied zone, which lead to better comfort as per ASHRAE recommendation. REFERENCES ASHRAE ANSI/ASHRAE Standard , Standard Method for Temperature Measurement, Atlanta: ASHRAE ANSI/ASHRAE Standard , Method of Testing for Room Air Diffusion, Atlanta: ASHRAE ANSI/ASHRAE Standard , Ventilation for Acceptable Indoor Air Quality, Atlanta: ASTM standards Inter-laboratory Cooperative Study of the Precision of the Determination of Average Velocity in a Duct Using ASTM D DS 555-S7 American Society for Testing & Materials Baughman AV. and Arens EA. Indoor Humidity and Human Health Part 1: Literature Review of Health Effects of Humidity-Influenced Indoor Pollutants, ASHRAE Transaction, 2000 pp Fisk W., and Rosenfeld A Improved productivity and health from better indoor environment. Centre for Building science Newsletter, Lawrence Berkely National Laboratory, summer Fountaion ME. et al, An Investigation of Thermal Comfort at High Humilities, ASHRAE Transaction, pp Fisk WJ How IEQ affects Health, Productivity, ASHRAE Journal, may pp Grimsrud DT. and Hadich DE., Residential Pollutants and ventilation strategies: Volatile Organic Compounds and Radon, ASHRAE Transactions, 1999, pp Kalaiselvam.S., et al Indoor Air Quality Studies, Report submitted to ISHRAE, Anna University. Loudermilk KJ Underfloor Air Distribution solutions for open office Applications, ASHRAE Transaction, pp Lu WZ., et al CFD Modeling and Measurement of Aerosol Particle Distributions in Ventilated Multizone Rooms, ASHRAE Transactions, pp Singh J Health, comfort and productivity in indoor environment, Indoor Built Environment vol 5: pp U.S. Environmental Protection Agency, Office of Air and Radiation. Indoor Air Facts No. 4: Sick Building Syndrome, revised,