Issue link: https://hi.iaq.net/i/630729
104 Section 7 handling of the problem. Ongoing (but reduced) complaints could also indicate that there were multiple IAQ problems and that one or more problems are still unre- solved. However, it can be very difficult to use measurements of contaminant levels as a means of determining whether air quality has improved. Concentrations of indoor air pollutants typically vary greatly over time; further, the specific contaminant measured may not be causing the problem. If air samples are taken, readings taken before and after mitigation should be interpreted cautiously. It is important to keep the "before" and "after" conditions as identical as possible, except for the operation of the control strategy. For example, the same HVAC operation, building occupancy and climatic condi- tions should apply during both measure- ment periods. "Worst-case" conditions identified during the investigation should be used. Measurements of airflows, ventilation rates, and air distribution patterns are the more reliable methods of assessing the results of control efforts. Airflow mea- surements taken during the building investigation can identify areas with poor ventilation; later they can be used to evaluate attempts to improve the ventila- tion rate, distribution, or direction of flow. Studying air distribution patterns will show whether a mitigation strategy has success- fully prevented a contaminant from being transported by airflow. Persistent Problems Solving an indoor air quality problem is a cyclical process of data collection and hypothesis testing. Deeper and more detailed investigation is needed to suggest new hypotheses after any unsuccessful or partially-successful control attempt. Even the best-planned investigations and mitigation actions may not produce a resolution to the problem. You may have made a careful investigation, found one or more apparent causes for the problem, and implemented a control system. Nonethe- less, your correction strategy may not have caused a noticeable reduction in the concentration of the contaminant or improvement in ventilation rates or efficiency. Worse, the complaints may persist even though you have been successful at improving ventilation and controlling all of the contaminants you could identify. When you have pursued source control options and have increased ventilation rates and efficiency to the limits of your expertise, you must decide how important it is to pursue the problem further. If you have made several unsuccessful efforts to control a problem, then it may be advisable to seek outside assistance. The problem is probably fairly complex, and it may occur only intermittently or cross the borders that divide traditional fields of knowledge. It is even possible that poor indoor air quality is not the actual cause of the complaints. Bringing in a new perspective at this point can be very effective. The next section provides guidance on hiring professional indoor air quality assistance. An interdisciplinary team (such as people with engineering and medical or health backgrounds) may be needed to solve particularly difficult problems. If you have made several unsuccessful efforts to control a problem, then it may be advisable to seek outside assistance.