Due to battling for a year and a half with my insurance company, we have been out of our mold-infested home due to mold-related illness.  We have done all of the removal ourselves using the NYC guidelines.  Is there a post-remediation clearance test we can do ourselves to test the spore count in the air?  Testing in our home is $1200, and we can’t afford that.  Do you have any recommendations?-Mary 

Because of the continual exposure of non-living areas such as crawlspaces, attics, and garages to the outdoor environment, is clearance testing worthwhile?  If so, why?-Chad, Virginia 

            In response to the first question above, there are no inexpensive tests that homeowners can do themselves to determine the effectiveness of a remediation.  As I will explain below, clearance testing even when conducted by professionals may in many cases be not much better.

            Chad poses a very interesting question, one that is seldom if ever addressed by professionals—that is, how worthwhile is clearance testing?

            Clearance testing is valuable in that it provides at least some information on the effectiveness of a remediation.  If the clearance results are but a fraction (i.e.) 5% of pre-remediation test results, then the remediation appears to have been quite successful.  If Stachybotrys spores are airborne even after remediation, additional cleaning steps should be implemented.  I recommend two 0 Stachybotrys slide samples post-remediation to achieve clearance on this species.

            Some homeowners seem to think that clearance implies that after remediation, there such be 0 mold.  That is unattainable for a variety of reasons.  One of these is that because many mold spores are very small, it is virtually impossible to collect and remove every last one.  In addition, the outdoor environment can and is an important source of mold in indoor spaces, particularly those buildings/dwellings that open windows for ventilation.

            Outdoor spore counts in the summer and fall can be enormously high.  I have measured outdoor mold concentrations here in the Midwest that on both volumetric culture plate and total mold spore methods are in the tens of thousands range.  Those spores do come indoors through open windows and doors and affect indoor concentrations for months.  Though crawlspaces, attics and garages are often open to the outdoor environment, entry of outdoor spores through these building areas is minor compared to having windows open during warm/moderate weather conditions.

            Then there is the question of undercounts.  In my position, I often get to see the test results of other professionals and the laboratories that support them.  I continue to be amazed at the very low spore count numbers that are reported.  I have been in houses that other professionals have tested.  My counts are often several times to an order of magnitude higher.  My volumetric plate counts are at times higher than total mold spore concentrations reported by others.  This may be due to chance or it may be due to the fact that counts commonly reported are very conservative and may indeed be undercounts. 

How good is clearance testing if the airborne mold counts are very low because of undercounts?  Not much better than if one does the clearance testing one’s self with a not very reliable technique?

January 23, 2004      

Indoor Environmental Quality (2000), Thad Godish Ph.D., C.I.H

Direct E-mail 00tjgodish@bsu.edu