Indoor Air Quality

Indoor Air Quality Investigation at Madison Area Technical College

by John W. Martyny, Ph.D., CIH, National Jewish Medical and Research Center, 1400 Jackson Street , Denver, CO  80206

posted by the MATC Environmental Health and Safety Office

Report Content:

Introduction:

• Previous IAQ Surveys
• Building Investigation

Methodology:

• Tracer Gas Studies
• Particulate Levels
• IAQ Measurements
• Bioaerosol Sampling

Results:

• Air Handler Inspection
• Carbon Dioxide Levels
• Temperature and Relative Humidity
• Bioaerosol Sampling
• Particulate Levels
• Air Movement Investigation

Conclusions

Recommendations

Title: Indoor Air Quality Investigation at Madison Area Technical College

by John W. Martyny, Ph.D., CIH, National Jewish Medical and Research Center, 1400 Jackson Street , Denver, CO  80206

Introduction:

This indoor air quality investigation was conducted at the request of Ms. Cynthia Eghbalnia, the District Safety Manager for the Madison Area Technical College (MATC).  The request was related to indoor air quality complaints that had been received from several areas of the building on an ongoing basis since the occupation of the MATC building in October, 1986.  At least two symptom surveys for Room 159 had been conducted through the Safety Office in order to help define the scope of the indoor air quality (IAQ) problems at the College but no definitive resolutions to the complaints had been achieved.  In addition to our investigation, the National Institute of Occupational Safety and Health was to conduct an investigation immediately following ours and the Wisconsin State Health Department was in the process of reviewing a third symptom survey in the facility.

 This IAQ investigation was conducted from 6/19/00 to 6/21/00 at MATC and specifically addressed four rooms within the facility (159, 214/215, 211, and 362).  The investigation included a visual inspection of the HVAC system at the College as well as an evaluation of the general indoor air quality utilizing a tracer gas system, an IAQ monitor, and a measurement of the particulate levels within the building.  In addition, samples for fungal levels were obtained at several areas within the facility.

Previous IAQ Surveys:

The results of 2 previous IAQ symptom surveys involving personnel from Room 159 of the MATC building were provided for our review prior to our investigation.  The initial survey was conducted in October, 1997 and was initiated because of complaints from staff regarding IAQ issues.  The questionnaire was distributed to all full-time staff working in room 159 (~ 60) with 54 individuals returning the questionnaire (a 90% return rate).  It appears that the questionnaire was self-administered and was provided to the individuals for return at a later date.  The questionnaire was primarily a list of symptoms that requested the individual to identify those symptoms that they had experienced and, if they had experienced these symptoms, to identify the frequency.  Several other questions were also posed at the end of the questionnaire in an attempt to determine possible reasons for the complaints or a pattern to the complaints.  

The most common daily complaints or symptoms listed were congestion/stuffy nose complaints (37%), temperature concerns (35%) and dryness complaints (44%).  Other conditions that were reported to occur in over 20% of the employees on a daily basis were eye irritation (30%), Headache (24%), and dry eyes (31%).  Eighty seven percent of those returning the questionnaire reported that they had not noticed any musty smells associated with the building and most individuals indicated that the air was not humid (83%).  In addition, most individuals indicated that they did not experience any fever or chest tightness associated with the building.  A number of the written comments were concerned about comfort conditions such as stuffiness, temperature, or air quality.  Although slightly less than ½ of the respondents reported allergies, no comparison was conducted between symptoms of allergic respondents as compared to symptoms of non-allergic respondents.  Allergic respondents typically have significantly complaint rates than do non-allergic respondents and therefore a high frequency of allergic individuals within an area may result in higher than normal complaint rates.  

The second survey was conducted in January, 2000.  This survey was designed as a follow-up to the initial survey and again consisted of a self-administered survey similar to the initial survey.  In this case, only 24 of the approximately 60 surveys handed out were returned for a return rate of only 40%.  This low return rate obviously precludes any authoritative analysis of the data but, in general, most of the complaint were similar to those on the initial survey with the exceptions being a rise in complaints regarding fatigue and drowsiness.   

In both symptom surveys, the questionnaire was provided to the employees and returned at a later date via campus mail.  In the second survey, the questionnaire was mailed to the employees and then returned.  Questionnaires completed in this fashion have somewhat less reliability than do questionnaires that are interview administered and returned immediately.  With that in mind, however, I would make the following observations:

Based on symptom surveys that National Jewish Medical and Research Center has conducted, the complaint levels do not appear to be exceptionally high.  In a study where we elicited both comfort complaints and work-related symptoms from teachers in grade schools within the Denver Metropolitan Area on three different occasions, we found the following frequencies of complaints: 

These complaint levels were obtained using a self-administered questionnaire that was given out and collected at a staff meeting.  The buildings were not necessarily problem-free buildings but, rather are representative of the responses that one would expect utilizing our questionnaire in grade schools within Colorado.  Other researchers have found similar levels in both problem (1,2,3) and non-problem buildings (4,5) as shown below. 

1 – NIOSH study of an office building in Harrisburg, PA.            

2 – NIOSH study of 85 office buildings.            

3 – NIOSH study of an elementary school in Caldwell, OH            

4 – Study of 4 N.J. office buildings by A. Hedge, Cornell            

5 – EPA BASE study, first 13 buildings.

The highest complaint rates reported in the surveys conducted at MATC were complaints of headache, eye irritation, etc. that are frequently caused by irritation.  Irritational symptoms may be caused by low levels of chemicals or particles in the room air.  Complaints of musty odors and high humidity (frequently encountered in the case of fungal contamination) were not  commonly reported at MATC.  Symptoms of fever and chest tightness, commonly observed in cases of hypersensitivity pneumonitis, were also not widely reported in the symptom survey.  

In order to best determine the meaning behind the MATC symptom survey results, it would help if the exact same questionnaire could be given in the same manner to similar individuals located in an area that was not considered to have an indoor air quality problem.  In this manner, the specific survey could be calibrated to the frequencies that might be expected in a non-problem area within your building.  You may find, however, that the differences are not will statistically significant.

Building Investigation:

A visual inspection of the MATC building was conducted on the initial day of the 3-day IAQ investigation (Monday, June 19, 2000).  This investigation was conducted in order for us to become acquainted with the building as well as with the HVAC system present within the building.  The air handlers were primarily located on the 2^nd and 3^rd floors of the building with the air handlers supplying the 1^st and 2^nd floors being located on the 2^nd floor and the air handlers for the 3^rd floor being located on that floor.  The air intakes for the air handlers used to be on the side of the building, but they had been ducted upward and now pull outside air primarily from the roof.  None of the exhaust stacks on the roof were observed to be in close proximity to the air intakes (25 feet or less).

A number of the air handlers were visually observed for operating conditions.  In general, the air handlers were in relatively clean condition with all filters intact.  We were informed that the air filters utilized were Mark 80 Purolator air filters with a 25 – 35% average efficiency and a 90 – 93% average arrestance.  Similar filters have been utilized since the building was built.  All of the air handlers were observed to have significant amounts of water in the condensate drain pans.  Some of the drip pans were also observed to have a significant amount of material collected in the drip pan suggesting that water has been present for long enough intervals to support microbial growth.  No biological samples were obtained from the drip pans due to interpretation difficulties with this type of data.  

The HVAC system at the college is a variable air volume (VAV) system with reheat coils in those ducts that are primarily located in areas with outside walls.  The air handlers are generally designed to bring in a minimum outside air volume of 10 – 15% , although in some areas, air handlers may bring in as much as 50% outside air on a constant basis.  The air handlers utilize chilled water to provide cooling however no water comes into contact with the air stream with the exception of the water in the drain pans.  No major water leaks were reported although there have been some broken heating coils as well as a few rainwater leaks.  Roofing repairs have reportedly reduced rainwater contamination.

The MATC building is made up of one main 3 story building and three single story wings that house the shop areas.  It was reported that, in general, the areas that would tend to generate odors (diesel repair, veterinary technology, print shop, etc.) had ventilation systems that were isolated from the rest of the building.  A number of these industrial or shop areas were in the wings, but some were in the main building (veterinary labs, print shops, chemistry labs, biology labs, etc.). 

The areas that had been previously been targeted as IAQ problem areas were primarily office areas.  Room 159 is an Admissions and Counseling Area that houses approximately 60 full-time staff.  Some staff have private offices whereas others are located in the larger center areas of the room.  The HVAC system provides air both to the large central areas and to the smaller rooms through the use of VAV boxes.  The smaller rooms do not appear to have a means of exhaust to the return air but the plenum may act in this manner.  Copiers and laser printers are scattered throughout the office area but seemed to have minimal utilization at the time of our investigation.  The entire area in Room 159 is carpeted and has cellulose ceiling tiles.  No significant water damage was observed at the time of our inspection.  

During our inspection of the facility, staff were generally present within Room 159 although the staffing level may have been low since summer school was just starting at the time of the investigation.  Other areas of the building, especially the instructor offices, seemed to be vacant at the time of our investigation.  Staff that were interviewed in Room 159 suggested that the air was stuffy and that they could frequently smell odors from the Veterinary Technician/Lab Animal Technician Program Area, as well as other areas of the facility.  Individuals also indicated that a number of staff members had suffered some building related illness and were concerned about heart attacks and sarcoidosis.  There was some use of personal room air cleaners and purifiers within Room 159.  

The offices of primary concern on the 2^nd floor were located in the northwest portion of the main building.  Room 211F is a staff office area where individuals are housed in cubicles within the room.  The cubicle partitions are relatively high and the area is carpeted.  No staff were present within the room while we conducted our sampling.  Room 214 houses three persons in a relatively cramped area.  Individuals were present in this room during sampling but they were not interviewed.   

Room 362 on the third floor was also a concern area.  This area is a teacher office area that is divided into a number of cubicles.  The area is carpeted and air is supplied throughout the room.  Staff were generally not present during our testing of this area and no complaints were received by us.  No water damage was observed during our visit to this area.

Discussions with the Facilities Administrator, Mr. Terry L. Gulmire, and his staff suggested that they had received ongoing complaints regarding the indoor air quality of the building.  Mr. Gulmire felt that the complaints began when the building was initially occupied in October, 1986.  This initial occupation occurred prior to the building being actually completed, which occurred in March, 1987.  Construction continued during this initial occupancy and may have resulted in significant odors being present within the building.  It was also possible that, in some cases, the outside air contained odors of diesel smoke both from MATC as well as some of the neighboring companies.  

Methodology:

Tracer Gas Studies:

Although a number of tracer gases can be used, we use a gas called sulfur hexafluoride (SF₆).  Sulfur hexafluoride is a gas that is odorless, invisible, and is not normally found in the environment.  It is also easy to detect and, with the use of a portable gas chromatograph, we can typically detect levels as low as 200 parts per trillion (ppt).  The gas is also very inert and has an allowable exposure concentration that is very high (1000 parts per million).  The high detection capability that we have allows us to use levels in the 200 part per billion (ppb) or less range for testing which is a factor of 5000 times below the allowable exposure level suggested by the American Conference of Governmental Industrial Hygienists.  This also allows us to conduct testing while personnel are working in the area.

Two methodologies were used in this tracer gas testing effort.  Both processes involved injecting tracer gas into the air, allowing it to mix, and then conducting specific tests on the gas.  Tests involved determining how long the gas stayed in the area and where it went after leaving the area.  The first tracer gas testing conducted enabled us to determine the number of outside air changes in the room tested.  In this situation, enough tracer gas was released to achieve a concentration of over 10 ppb.  The gas was allowed to mix and then a gas chromatograph was used to monitor the decline in the concentration of SH₆.  The gas chromatograph utilized was a Model 101 Autotrac Tracer Gas Monitor manufactured by Lagus Applied Technologies in San Diego, CA.  This gas chromatograph is capable of automatically sampling the air remotely through plastic tubes attached to the automatic sampler.  In some areas, we also used syringes to sample for the concentration and injected the air directly into the gas chromatograph.   

The number of air changes in the areas monitored was calculated by determining the rate of decline in the natural log of the SF₆ concentrations, plotting the result over time and conducting a regression to determine the slope of the line.  In this manner, the number of air changes can be  determined for each specific point monitored as well as for the total area monitored.  The air change rates for each of the sampled locations can be compared to determine if the air is being distributed to the area in an efficient manner or if some areas are experiencing fewer air changes.   

The second type of tracer gas testing that was conducted was to use the tracer gas to determine if there was a ventilation connection between two areas.  In this case, the tracer gas was injected into the area in question (such as the Veterinary Technician/Lab Animal Technician Program Area)  at a concentration of approximately 200 ppb.  After mixing, other areas of the building were tested in order to determine if the gas had spread to those locations.  The presence of SF₆ in an area remote from the area in which the gas was injected indicates a ventilation link.  The speed of the travel and the concentration at which the gas arrives also gives some indication of the type of connection.  A direct connection has a faster arrival time and a higher concentration than does an indirect source such as re-entrainment from an exhaust system.

Particulate Levels:

Another factor sometimes utilized to describe indoor air quality is particulate concentrations in the indoor air.  Particles generated by smoking and combustion have been found to heavily influence indoor air particulate levels and have been implicated as carriers for other allergens.  In addition, man-made mineral fibers in dust, originating from thermal and acoustic insulation as well as ceiling tiles, have been associated with sick building syndrome symptoms in some buildings.  Particulate exposure has also been correlated with increased prevalence of headache as well as increased overall complaint levels.  Several studies have documented the indoor migration of fine particles (less than or equal to 2.5 um in aerodynamic diameter) generated by fossil fuel combustion in the outdoor environment.  Indoor generation of particles have been linked to smoking, cooking, and human activity. 

Several studies have compared indoor particulate levels to outdoor particulate levels by calculating a ratio of the indoor to outdoor particulate levels.  One researcher indicated that in homes with no activity, the indoor/outdoor particulate ratio was approximately 0.7 for PM10 particulates (outside levels were slightly higher than inside levels).  Smoking within the building increased the ratio to greater than 1.8 indicating that the inside levels increased to almost twice the outdoor levels.  Most homes, as expected were close to or slightly less than 1.0 indicating that inside and outside levels were very similar.  

The primary factors influencing the particle ratios are the particle size of interest, the air exchange rate of the building, and the surface to volume ratio of the indoor environment.  Buildings with a lower air exchange rate have indoor air particulate levels that are less reflective of outdoor levels than do buildings with higher ventilation rates.  Studies within Utah classrooms found that student activities increased the number of coarse particles in the air and reduced the correlation between indoor PM 2.5 and outdoor PM 2.5.  Other researchers have also found this link between activity in a building and coarse particle generation.  

There have been relatively few school studies where particle concentrations have been measured.   In one study, 8-hour averages of respirable suspended particulate matter (RSP) (particles with a mass median aerodynamic diameter equal to 3.5 µm) ranged from less than 11 to 40 µg/m³.  Studies conducted within classrooms in Hong Kong have determined that PM 10 levels in classrooms frequently exceeded the current government standard.  These findings were coupled with CO₂ levels that were elevated, suggesting poor ventilation rates within the classrooms.  Another researcher found that there was a positive correlation between settled dust levels in school and subjective and objective reports of nasal congestion.  This finding suggests that coarse particulate levels within some schools may be related to health complaints.  

Particulate sampling during this investigation was conducted using a Model 3320 Aerodynamic Particle Sizer, manufactured by TSI, St Paul, MN.  The Model 3320 utilizes time-of-flight sizing technology to obtain accurate particle counts and sizing information.  The instrument counts and sizes particles that range from 0.5 um to 20 um in diameter.  The data obtained can be downloaded to a computer and manipulated utilizing application software to determine the characteristics of the aerosol present within a space.  During this investigation, samples were obtained from a number of the areas of concern as well as the outside.  Total amounts of particulate as well as the size of the particulate was determined and compared to the outside particulate level.  Generally particulate was grouped as PM2.5 or PM10.  PM 2.5 includes those particles with an aerodynamic diameter of 2.5 um or less and PM10 includes all particles with an aerodynamic diameter of 10.0 um or less.  PM10  particulate therefore includes the PM2.5 particulate.

IAQ Measurements:

Indoor carbon dioxide levels are commonly utilized as a surrogate for measuring outdoor air intake rates.  In schools, the CO₂ concentrations that have been reported suggest that many classrooms do not meet the ASHRAE standard 62-1989 for minimum ventilation rates, at least part of the time.   These higher levels of CO₂ in schools may be influenced both by occupant density and inadequate outdoor air supply.  Godish et al  found CO₂ levels exceeding 2500 ppm in university classrooms where a VAV system was operating outside of the design specifications.  Modifications to the system reduced the CO₂ levels to below the ASHRAE guidelines of 1000 ppm.  In another study of both mechanically and naturally ventilated classrooms, researchers found CO₂ levels exceeding 7000 ppm in naturally ventilated classrooms and as high as 3500 ppm in the mechanically ventilated classrooms. Other reasearchers have reported CO₂ levels exceeding 2000 ppm in inadequately maintained ventilation systems.

Bioaerosol Sampling:

Bioaerosols are defined as any aerosol of biological origin.  Bioaerosols may consist of parts of organisms such as bird feathers, cat dander, cell walls of gram negative bacteria, etc.  They may also consist of the entire organism as in the case of bacteria or they may exist as reproductive portions of the organism as in fungal spores.  In addition, many byproducts of organisms such as mycotoxins or microbiological volatile organic compounds (MVOC’s) are may also be considered bioaerosols.  

Since most bioaerosols are composed of relatively small particles, they are usually respirable and the primary route of exposure is via the respiratory tract.  Bioaerosols cause three primary health effects: infections, toxic reactions, and allergic reactions.  Infections are caused by pathogenic organisms that are taken into the body and are able to grow and proliferate resulting in a specific illness.  Examples of infections are tuberculosis, colds, flu, strep. throat, etc.  Infections are frequently spread by person to person contact and are less likely to be a building related concern.  In fact, infections are more likely to be related to the number of personal contacts then to conditions within a building.  Individuals with a high degree of person to person contact are more likely to have higher infection rates than are individuals whose job requires little contact with coworkers or the public.  

Toxic reactions from bioaerosols are not commonly recognized at this time although some work with endotoxins produced by gram negative bacteria has been conducted.  In a few cases, mycotoxins from fungi have also been implicated as a cause of illness in exposed individuals.  The most publicized case of a possible mycotoxin reaction was the association between a lung illness in infants and the growth of a specific type of fungi (Stachybotris chartarum) in Cleveland, OH.  There has been some concern that, although there was an association, it was not a causal association.  These toxic reactions may be attributed to building conditions if the building is supporting large amounts of microbiological growth.  

The most common health effect from bioaerosols is an allergic reaction.  One of the most common examples of this type of reaction is hay fever.  Hay fever is a reaction to outdoor plant pollens and fungal spores experienced by many individuals on an annual basis.  Illnesses such as hypersensitivity pneumonitis and allergic rhinitis are also common allergic reactions caused by exposure to bioaerosols.  These illnesses are usually caused by exposure to higher than normal levels of microorganisms and may be associated with increased bioaerosol exposure in a specific building. 

Two types of sampling are routinely conducted when sampling for bioaerosols.  Non-viable bioaerosol sampling can be conducted utilizing a number of sampling methods that impact air onto a greased slide.  The greased slide can then be shipped to a laboratory where the slide is stained and the captured spores identified.  This method does not require the spores to grow and is therefore not subject to the growth requirements of the species present.  The downside of this type of sampling is that identification of the exact species present is not always possible.   

Viable samples are obtained by impacting the air onto a growth media.  The media is then sent to the laboratory and grown for a specified amount of time.  The colonies that grow are identified to species and counted to determine the amount of mold spores per unit of air.  This methodology enables better identification of the fungi present in the air but requires that the media utilized fit the fungi that is present.  If the wrong media was used, then no growth may occur even though high levels of microorganisms may exist.   

Regardless of the type of sampling conducted, the validity of the results is proportional to the number of samples taken and the different times during which they were taken.  A large number of samples taken over a long period of time provides a higher degree of accuracy than does a single sample taken on one day.  The risk of a health effect is related to the concentration of fungi present and not to a species of fungi.  Most cases of bioaerosol illness are found to be caused by common molds such as Penicillium sp., Aspergillus sp., etc. and not a specific toxic species.  Therefore the determination of a bioaerosol problem is related to an increase in the concentration of a bioaerosol in relation to outdoor levels.  An increase in indoor levels of total bacteria or fungi or an increase in a specific species of microbe may indicate that the building is growing that microorganism or that group of microorganisms.  This situation is may increase the risk of illness associated with that bioaerosol exposure.

The bioaerosol samples taken at MATC were taken using an N6 Anderson Cascade Impactor that was calibrated to sample at one cubic foot per minute (28.3 lpm) onto a Rose Bengal Agar plate.  Two plates were sequentially taken at each sampling point.  One plate was sampled for one minute and the other plate for two minutes.  Each sampling location was sampled both in the morning and in the afternoon for a total of 20 samples.  Samples were also taken in the outside air during both sampling periods for comparison.  The samples were shipped by overnight mail to PathCon Laboratories for analysis.  Analysis was confined to fungal species since bacteria are rarely found to be a cause of building IAQ problems. 

Results:

Air Handler Inspection:

In general, the air handlers were found to be in good condition with good filters provided.  The air handlers were generally in clean condition and the filters appeared to be in good shape on the air handlers that were inspected.  The actual filter change and servicing dates were not evident on the air handlers but we were informed that data on each of the air handlers was available and that filters were changed on a regular basis.  The filters provided were pleated filters with a reasonable efficiency (greater than 40%) for particles of greater than 1 um in diameter.  The filters were installed in a manner such that both the outside and return air were filtered.  Excessive amounts of dirt were not noted on the supply air louvers present in the offices inspected, suggesting that filtration was adequate.  

The primary concern regarding the air handlers was the presence of water in the drip pans of air handlers.  All of the air handlers observed had significant amounts (an inch or so) of water in the drip pans.  In many cases, this water was observed even though no water was leaving the drain pipes into the drain.  In addition, when the air handler was shut off, the drain pan still did not drain.  I some cases the drip pan was relatively clean but in other cases, the drip pan appeared to have a microbiological slime associated with the water.  Visible mold growth was not noted in any other areas of the air handler, but few areas were visible at the time of our investigation.  Water did not appear to have moved to the exhaust side of the air handler but, again, these areas were not easily visible.  A biocide was also used in most of the drip pans.  This practice does allow biocide to enter the air stream in the air handler. 

The internal fiberglass lining in most of the air handlers seemed to be in good condition, although, one air handler had experienced roof damage and did have some fiberglass lining damage.  Fiberglass entering the air stream typically causes a dermatitis and itching problem which did not seem to be reported at MATC.  Damaged fiberglass linings should be fixed as soon as possible to assure that skin irritation does not become a concern.

Carbon Dioxide Levels:

The carbon dioxide levels obtained within the facility were relatively low.  The carbon dioxide levels obtained were as follows:               

These levels of carbon dioxide indicate that there is very little buildup of carbon dioxide within the building.  All of the measurements are well within the current ASHRAE guidelines of below 1000 ppm and below the proposed OSHA guidelines of 800 ppm.  An investigator could infer that the low carbon dioxide levels indicate an adequate outside air supply however in order to make this statement a number of other factors must be evaluated.  The use of carbon dioxide as an indicator for adequate ventilation rates is predicated on the fact that an adequate supply of humans are present within a specific area to generate enough of a tracer gas (carbon dioxide) to predict a ventilation rate.  The individual concentration needs to be adequate for the entire area ventilated by the air handler and not just the room measured.  Low carbon dioxide levels in an area with a low density of  people present may not indicate an adequate ventilation rate.

During this investigation, the actual numbers of individuals present were lower than normal in the school as a whole, since the summer term was just beginning.  Most classrooms were empty and a number of the offices were unused, thus the use of carbon dioxide to determine air exchange rates was not justified.

Temperature and Relative Humidity:

Temperature levels within many of the complaint areas were relatively high on both of the days in which we tested the room air.  The levels obtained during the time that the rooms were sampled were as follows:

The temperature in Room 159 was generally between 72^o F. and 74^o F. during the time that the room was occupied on Tuesday morning and stayed above 74^o F.  until personnel left at the end of the day.  Room 362 had relatively low ambient temperatures, however, the room was completely empty during most of this investigation.  Room 214 had three people in the small room for the entire time that the measurements were made and the room was perceptively hot at the time.

Relative humidity levels were also high during the investigation period.  The relative humidity levels were as follows:

Increased humidity levels combined with higher temperature levels can result in discomfort among employees.  In general, temperatures were frequently in the mid 70 ^o F. range and relative humidity was generally in the 80 % relative humidity range.  ASHRAE Standard 55-1992 Thermal Environmental Conditions for Human Occupancy suggests that the summertime temperatures should be held between approximately 73^o F. and 78^o F. when the relative humidity is between 70% and 80%.  Even at this level, up to 20% of individuals may be unhappy with the temperature.

Bioaerosol Sampling: 

A total of 22 samples were submitted to PathCon Laboratories for analysis.  Two of the plates that were submitted were blanks and had not been exposed to the outside air.  The results of the sampling were as follows:

CFU = Colony Forming Unit (essentially a spore) These results indicate that the levels of fungi found inside of the facility were significantly lower than those found outside of the facility and, in addition, the species are similar to the outside levels suggesting that fungi species are not propagating within the MATC building.  This sampling reflects the conditions existing during the period during which we sampled and therefore does not indicate that no bioaerosol problem exists but rather that no bioaerosol problem was detected during our sampling.  These results should be compared to the results obtained by NIOSH from their sampling conducted the next week.

Particulate Levels:

Suspended particulate levels were obtained from three locations from within the building and from one location from outside of the building.  The particulate levels were broken down into PM 2.5 and PM 10 groups.  The PM 2.5 information pertaining to those particles with an aerodynamic diameter of 2.5 um or less while the PM 10 group pertains to those particles with aerodynamic diameters of 10 um or less.  The results that were obtained are as follows:

In order to more easily understand the data, we calculated a ratio of the inside to outside suspended particle mass by dividing the inside mass by the outside mass.  This calculation provides a clearer picture of the contribution that the building makes to the observed particulate level.  The results of this calculation were as follows:

PM 10 levels can generally be expected to range from 5 ug/m³ to 28 ug/m³ in normal buildings.  The levels obtained at the MATC building are well within that range suggesting that the building is not a “dusty” building.  There was a significant difference between the values obtained in Room 159 and the other areas sampled with both the actual concentrations and the ratios being much higher in Room 159.  Two factors can cause this difference, activity and air exchange rate.  A higher activity rate within a room may result in an elevation of the particulate level, especially the larger particulates (PM 10).  A low air exchange rate may hold the particles in the area longer and again result in a higher particulate concentration.  It is interesting that not only the larger particles are increased but also the smaller particles.  It is possible that the elevated particle concentrations are influenced by both of these factors.  Room 214 and Room 362 had very little activity while we were sampling in the rooms.  Room 159, on the other hand, had a reasonable amount of activity and, in addition, had many different office machines that may have introduced not only larger but also smaller particles into the room air.  Laser printers and copy machines, in particular, may cause an increase in the airborne smaller particle levels.

Air Exchange Rates:  

The primary room that was tested to determine air exchange rates was Room 159.  This area had the largest number of employees present at the time that our testing was conducted and is one of the major areas of concern.  During our stay, we conducted a total of four tracer gas releases for air exchange rates within Room 159.  During each of these releases, nine specific areas were monitored using the automatic sampling mode of the gas chromatograph.  The areas sampled were chosen to give us a good picture of the average air exchange rate for the room as well as to determine how that rate varied between the individual offices or the two major work areas.  The locations that were sampled were:

The initial test was conducted on 6/20/00 in the morning.  The injection of tracer gas was made into Air Handler #5 at approximately 9:50 am.  The gas was given time to mix and sampling was initiated at approximately 10:15 am.  The results of this initial run was as follows:

The air exchange rate is the total volume of air entering Room 159 that did not have an associated concentration of sulfur hexafluoride tracer gas.  The majority of this air is likely to be outside air.  The air exchange rate therefore measures the approximate amount of outside air entering the room.  The R² value gives an idea of how reliable the data is by indicating how much of the variance is predicted by the equation.  R² values in the 0.95 range or above are what we normally expect, meaning that the equation predicts about 95% of the variance of the sample.  R² values of greater than 0.99 are not unusual using this technique. 

During this first test, the air exchange rates were relatively high but the R² values were relatively low.  A visual look at the concentrations of tracer gas in the room over time suggested that the initial air exchange rate was much higher than the exchange rate later in the test.  This also explains why the air exchange rate lowered as the location number increased since the later locations were sampled at a later time.  In order to define this observation, we calculated the air exchange rates for a selected number of the sampling locations after 23 minutes and after 46 minutes.  The air exchange rates were as follows: