Indoor Air Quality

Report Title: Retest of Ventilation Parameters 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

Introduction:

A retest of the ventilation system parameters at the Madison Area Technical College (MATC) was conducted between October 10, 2000 and October 12, 2000 at the request of Ms. Cynthia Eghbalnia, District Safety Manager for the College. The retest followed an indoor air quality survey of the facility conducted in June, 2000 and reported in July, 2000. During that initial investigation, tracer gas studies were conducted within several areas of the College to determine outside air exchange rates. At the time, the hot temperatures, combined with the loss of a chiller resulted in the ventilation system being out of specifications and unable to maintain normal cooling and air circulation within the building. This retest was designed to look at the performance of the ventilation system at a cooler time of the year and at a time when all components of the ventilation system were in normal operation. In addition, classes were in session at the time of the retest and the results should approximate conditions present during normal occupancy and use.

Methodology:

This second round of testing was conducted in the same manner as was the initial testing. Tracer gas studies were conducted utilizing sulfur hexafluoride and a Model 101 Autotrac Tracer Gas Monitor manufactured by Lagus Applied Technologies in San Diego, CA. An AQ-501 was utilized to obtain carbon dioxide, relative humidity, and temperature levels within the College and a Model 3320 Aerodynamic Particle Sizer, manufactured by TSI, St. Paul, MN was used to determine particulate levels. Samples were taken utilizing the same or similar techniques as in the initial testing effort. In addition to the sampling, some of the air handlers were visually examined for moisture in the drain pans. None of the drain pans were found to contain moisture at the time of my inspection.

Results:

Tracer Gas Testing:

A total of four tracer gas tests were taken during this re-testing period. The initial test was conducted in the morning of October 11, 2000. This test was conducted under normal operating conditions and at similar locations to the first testing period. Samples were taken at the following locations:

1. Room 159 J
2. Center of the east corridor in Room 159
3. South end of the east corridor in Room 159
4. Room 159 O
5. The testing room
6. Front registration area
7. Center of the west corridor in Room 159
8. Room 159 S
9. Room 159 L

At the time of this test, the recorded parameters for the air handlers were as follows:

Table 1. Air handler parameters during testing on 10/11/2000.

The tracer gas results obtained in Room 159 ranged from 1.9 outside air changes per hour (oach) to 2.5 oach (Table 2). These outside air exchange rates are higher than the rates measured during the initial testing conducted in June, 2000 which were in the area of 1.0 oach.

Table 2. Outside air exchange Rates Measured at MATC
During Re-test in Air Changes per Hour.

Test 1. - Conducted in the morning of 10/11/00
Test 2. - Conducted in the afternoon of 10/11/00
Test 3. - Conducted in the evening of 10/11/00
Minimum Test - Conducted in the afternoon of 10/12/00
ND – Not Done

Immediately after the first sampling in Room 159, syringe samples were obtained from the following rooms in other areas of the building:

1. Room 362 A
2. Room 362 B
3. Room 215 A
4. Room 211 F
5. Room 214
6. Room 211 B

These rooms had also been tested during the initial testing period. The outside air exchange rates for these rooms were somewhat higher than were the outside air exchange rates in Room 159 and ranged from 3 oach to 4.8 oach.(Table 2) The outside air exchange rates observed during the initial testing period in June, 2000 ranged from 1.2 oach to 1.9 oach which was substantially lower than the rates observed during this testing period. During both the June and October testing periods, the outside air exchange rates in these rooms were found to be higher than the rates observed in Room 159.

A second round of testing was conducted in the afternoon on 10/11/00 with air handler parameters essentially the same as during the earlier sampling time. The sampling points in Room 159 were also the same. The results ranged from 2.2 oach to 2.6 oach which is only slightly higher than the outside air exchange levels measured during the morning hours. The other rooms were not tested during this sample run.

A third testing round was conducted during the evening hours with the testing starting at 6:00 pm local time. All of the air handler parameters were the same as in the previous two testing periods except at the end of the test when the system began to bring in less outside air. The outside air exchange rates ranged from 2.1 oach to 2.3 oach (Table 2), slightly lower than observed during the second test. The syringe samples were not taken during this sampling period. In order to determine the minimum outside air exchange rates expected for the rooms, a special sampling was conducted during the afternoon of 10/12/00. During this testing period, the air handlers were at their minimum outdoor air settings. The observed air handler parameters were as follows:

Table 3. Air Handler Parameters during Minimum Testing.

The outside air exchange rates in Room 159 ranged from 0.7 oach to 1 oach (Table 2) which is similar to the lowest rates observed during the initial testing period in June, 2000. The outside air exchange rates in the rooms sampled using the syringe samples ranged from 1.2 oach to 2.3 oach. These levels were also similar to the lowest rates observed during the initial testing period. This information seems to suggest that the outside air exchange rates observed during June, 2000 were relatively low rates for both of the areas tested and rates above 2.0 oach are the rates observed during “normal” operations. The r-squared values for all of the tests conducted during all four of the sampling periods were above .90 indicating good confidence for the calculated outside air exchange rates.

Particulate samples were taken using the Aerodynamic Particle Sizer manufactured by TSI in a number of rooms on October 11, 2000 and October 12, 2000. Samples were averaged over a five minute period. The results were as follows:

Table 4. Particulate Data Obtained at MATC.

The results of this sampling indicated a particulate aerosol ranging in mass from 3 ug/m3 to 19 ug/m3. Although the highest levels were found in Room 159, the levels overall are very low and do not indicate elevated indoor air particulate levels. Average buildings reported in the literature have particulate levels that range from 5 ug/m3 to 28 ug/m3, which is inclusive of the levels found at MATC. The higher levels in Room 159 may be explained by a higher amount of clerical work and equipment generating aerosols (printers, copiers, etc.) in that area than in other areas. Even the outside levels were very similar to the levels found in Room 159. The mass median aerodynamic diameter (MMAD) was also similar in most of the rooms tested and indicates that the aerosol in each room was similar. In addition, the mean particle size was about 0.8 um for all of the areas sampled. Particulate levels were higher in all of the rooms than those found in June, 2000 but the number of occupants within the school was higher. The increased usage of the school could easily explain the increased particulate concentration.

Carbon Dioxide Levels:

Carbon dioxide levels were obtained from the following locations using a Metrosonics AQ 501:1. Center of east corridor in Room 159
2. Center of west corridor in Room 159
3. Room 362 A
4. Room 215 A
5. Room 211 F
6. Room 214
7. Room 211 B

The range of carbon dioxide levels found within the different rooms were as follows:

All of these levels are below the current ASHRAE guideline of 1000 ppm and all but one were below the OSHA proposed guideline of 800 ppm. In this case, the 890 ppm level was only reached when the outside air intakes were closed. In fact, most of the levels presented were obtained during the worst case (minimum air handler setting) situation. These levels would not be expected during normal operations but yet, are still within normal ranges.

Air Temperature and Humidity:

Air temperature and humidity were taken at the same locations as were the carbon dioxide levels. The results were as follows:

The relative humidity levels were dramatically lower than during the summer sampling event. Maximum temperatures were also lower than during the June sampling period. Again these samples were taken, for the most part, when the air handlers were at the minimum outdoor setting and therefore represent worst-case figures. These levels are well within normal levels and should represent comfortable levels for most individuals. Conclusions and Recommendations

Based on the sampling that was conducted between October 11, 2000 and October 12, 2000, we can make the following conclusions:

• Examination of the drain pans in Air Handling Units 5, 8 and 13 indicated that the drain pans were all dry and clean. This is not unexpected since the outside air is substantially dryer in the fall and winter than it is in the spring and fall. Moisture in the drain pan is usually caused by cooling hot outside air resulting in a relative humidity increase to the point where moisture condenses from the air. This is not a concern in the cooler months.
• Under the “normal” operating conditions that were observed during this sampling period, the outside air exchange rates in Room 159 and in the other areas tested were in excess of 2 air changes per hour. In some of the areas, the outside air exchange rate exceeded 4 air changes per hour. These levels were approximately twice the levels measured in the summer and are within our suggested outside air exchange rates.
• Under minimum outside air damper conditions, the outside air exchange rate is similar to the rates that we observed during the summer sampling period (< 1 oach). These levels are lower than we would suggest for operations during most days of the year but may be acceptable for minimum operations as long as minimum operations do not become the norm.
• Carbon dioxide levels were below accepted maximum standards in this sampling as they were during the June sampling. One area did show carbon dioxide levels above 800 ppm (an OSHA proposed level) but that was during the time that the air handlers were at a forced minimum outside air setting.
• Temperature and relative humidity levels were lower than during the summer sampling period and were well within the range where most individuals should be comfortable. Some might suggest raising the humidity level but we would recommend against that practice since adding humidity to the building dramatically increases the possibility of microbial growth and the resulting bioaerosol concerns.
• Air migration testing between areas of the building was not conducted since changes to the ventilation system had not been completed at the time of this sampling effort.

Based on our testing during this re-test period, we would make the following recommendations:

• Monitoring of the ventilation system should be continued in order to determine the air flow for the system over time. If the conditions measured during this sampling period are the conditions that occur during most of the school year, then they should meet current standards and we would not suggest any further ventilation changes.
• If the ventilation conditions that we monitored this fall are not the conditions that exist during the majority of the year, changes to bring the system to 2.0 oach may be necessary. In other words, if the ventilation system can not normally provide 2.0 oach during most (approximately 80% or better) of the days in which the building is occupied, it should be modified to accomplish that goal.
• We would suggest that continued work be conducted to assure that odors and contaminated air from industrial-type areas not be allowed to migrate to office or classroom areas.

In general, the performance of the ventilation system was significantly improved from the first testing period in June, 2000. If this type of performance is maintained and infiltration of odors from other areas of the building is eliminated, indoor air quality perception should be improved. If there are any questions, or we can be of any further help, please let us know.