The following questions and answers have been posted from HTA field experiences and are offered here to participate in the on-going discussions of the many technically evolving viewpoints and decisions.  Where possible HTA has added links for the reader to further explore the HTA response:

• What are Building or Property Condition Assessments, Preliminary Site Assessments (Phase I or II), Engineering Building Inspections, or Engineering Physical Element Reports?
• What is moisture intrusion?
• What is a fenestration?
• What are the contributing factors leading to moisture intrusion associated with buildings?
• Are there moisture intrusion standards?
• Is concrete impervious to moisture and water?
• Is there just one agreed upon way to test water vapor transfer through concrete?
• Is testing windows, doors, or exterior walls with a garden hose and nozzle an acceptable practice to show leaks?
• How can building materials contain excess moisture?
• What are vapor barriers or weather resistive barriers and how significant are they?
• Can money be saved by having an engineering review of the plans and specifications for potential moisture intrusion prior to or during construction?
• What is mould?
• Why do you spell mold with a u (mould)? 
• Are bacteria and moulds the same?
• How does Lead or Asbestos experience help to address mould problems?
• What is the difference between remediation, abatement and mitigation?
• What causes mould to grow indoors?
• What is mould amplification?
• What is a significant difference?
• Is the mould indoors a more toxic mould than that found outdoors?
• What is the real problem with mould indoors?
• Are there real health effects from mould exposure to humans?
• What is the “black toxic mould”
• In the area of mold investigations and mitigation, which of the many certification designations are issued by the government versus trade and professional organizations?
• What is the difference from a government issued registration/certification and a trade/professional organization certification?
• What does this difference mean to me as a property owner/manager?
• Are there governmental statutes and regulations defining safe or hazardous levels of mould indoors?
• Are there government standard tests for mould?
• Are there government standard qualifications for commercial mould investigators or mitigators?
• Is removing and throwing away everything that may have come in contact with mould justified?
• Why are physical mould removal methods often used rather than disinfection?
• Is mould testing required to understand and correct an indoor mold amplification problem?
• What is a disinfectant?
• Is there a difference between a biocide and a disinfectant?
• Once mitigated, will mould return and amplify?

What are Building or Property Condition Assessments, Preliminary Site Assessments (Phase I or II), Engineering Building Inspections, or Engineering Physical Element Reports?
Building or Property Condition Assessments are documents prepared to generally meet the requirements of Standards such as ASTM E 2018 -01 by individuals experienced in the field and/or so certified by private authority bodies to provide owners or buyers an independent assessment of the usefulness of the features of the building.   Preliminary Site Assessments are documents prepared to generally meet the requirements of Standards such as ASTM E-1527-05 and may be part of real estate transactions or initial investigations required for hazardous waste sites by state and federal regulation.  California uses a Registered Environmental Assessor designation to identify those persons with minimum qualifications to prepare these reports.  Engineering Building Inspections or Engineering Physical Element Reports are documents prepared for owners by Registered Professional Engineers. Local Building Officials may specify the content of these reports. These documents focus upon the structural, mechanical, electrical and other engineering aspects of the building requiring the judgment of a Professional Engineer to render an opinion regarding the health and safety of the building.

What is moisture intrusion?
Water leaking into or water vapor condensing in buildings is generally addressed under moisture intrusion.  In theory some de-minimus building moisture intrusion is to be expected, but when the amount and the period of moisture intrusion extend to the point that building systems are damaged and health of occupants are  threatened that is the  moisture intrusion of concern.  The issues can be associated with roofs, walls, fenestrations, floors, plumbing, and HVAC. 

What is a fenestration?
Fenestration is an architectural term referring to the arrangement of windows in a wall.  From the Latin word, “fenestra,” meaning window. 

What are the contributing factors leading to moisture intrusion associated with buildings?
The complexity of moisture intrusion involves many aspects of work associated with the building including: design, specification of materials, manufacture of building systems, installation of building systems, maintenance of building systems, and repair or remodel of building systems.  Failures can happen at any stage and can be caused indirectly by non-moisture related building systems failing causing moisture related systems to also fail.

Are there moisture intrusion standards?
Yes.  There are Building Official Codes (Uniform Building Code [International Conference of Building Officials] + Local Codes), and governmental standards (state and federal associated with energy, plus 24CFR3280 - HUD Code) as well as manufacturer installation requirements, owner use limitations, and fundamental design principles that are standard to the building industry.  Standard setting bodies such as ASTM with Standard such as E- 2266-04 and E-241-04 continually offer guides to minimize moisture intrusion.

Is concrete impervious to moisture and water?
No.  Concrete can be made relatively impervious to both liquid and vapor water, but without these special preparation, both liquid and vapor water may move slowly through concrete.   A common view is that a normal dried concrete slab-on-grade may pass in the range of 2 – 3 pounds of water per day per 1000 sq. ft. of floor.  Experience has shown that indoor problems can be expected when the concrete water vapor transfer rate is in the double digit range.

Is there just one agreed upon way to test water vapor transfer through concrete?
No.  There are physical methods and electronic methods.  If feasible a portion of concrete is removed weighed, dried, and weighed with the difference (under controlled conditions) being the water contained in the concrete.  A known weight of a desiccant can be sealed onto the concrete enclosed in a known area for a know time to determine the amount of water vapor that was collected over time over the area.  Humidity can be measure under an impermeable barrier sheet sealed to the concrete surface to assess water vapor build up.  Electrical resistance changes can be measured between two pins to relate relative moisture present in the concrete.   While it is difficult to get direct correlation between measurements, these techniques do provide guidance and do agree upon trends observed.

Is testing windows, doors, or exterior walls with a garden hose and nozzle an acceptable practice to show leaks?
Not unless one wishes to disregard design, manufacturer, and installer objectives and assurances.  Fenestration systems are designed to resist moisture under known conditions of precipitation and wind (pressure differential).  Flooding a window or door with water from a hose provides no useful data pertaining to adequacy of design, installation or manufacture.  There are accepted methods of testing and guidance has been provided by ASTM E 1105-00; E – 547 – 00; E- 331-00; E 699-99 and other organizations such as American Architectural Manufacturers Association AAMA 502-02, or in Canada the Canadian Window and Door Manufacturers Association [section 8.0].

How can building materials contain excess moisture?
Moisture in a building can accumulate and dissipate in relationship to: outdoor moisture; indoor moisture; exfiltration of moisture, and diffusion of moisture.  The design, construction, and operation of the building are critical to controlling moisture accumulation.  Concrete, lumber and surfaces such as wall board or paneling, ceiling and floor coverings can all contain moisture depending upon manufacturing, transporting, storing, and using.   Unless lumber is kiln dried and protected from weather, the more common construction lumber used is green and therefore wet.   Treated wood containing 19% or more moisture is not considered acceptable. Temperature/ ventilation during construction and once the building is closed and occupied contributes to the moisture load within a building.  Concrete may take weeks to months to cure and for the vapor transfer rate to become within the normal range.  Adding moisture during construction in the form of water based light weight flooring, tape, texture, paint, adhesives, cleaning solutions and others all contribute to the water balance within a building.  Psychrometrics is the study of the physical and thermodynamic properties of air-water vapor mixtures that employ the use of Dalton’s Law and the Ideal Gas Law.   As building systems come in direct contact with liquid water or high levels of water vapor they can adsorb the water.  Temperature and moisture content of the indoor air and the building systems are in a continual state of reaching equilibrium. Higher moisture content of warmer air in contact with cooler building systems results in condensation of moisture and wetting of the building system.

What are vapor barriers or weather resistive barriers and how significant are they?
As water vapor routinely moves from a volume of higher water content to one of lower water content, a low permeability barrier is often used to retard or stop this movement. A vapor barrier is intended to block or reduce water movement in the vapor phase, while a weather resistive barrier is intended to “breath” but retard water penetration (UBC §1402, Chapter 14, Vol 1).   Vapor barriers may be used under slab-on-grade concrete, on exterior walls, and on ceilings

As water is seeking its lowest elevation point, weather resistive barriers are used to direct the water flow away from the building frame and contents.  A weather resistive barrier is typically the kraft paper placed on the frame of a wooden structure below the exterior siding or stucco.

While the use of these techniques is common place, there is less than total agreement on the placement and characteristics of vapor barriers.  There are local circumstances that support the vapor barrier placement close to the occupied side of the wall and others that argue placing the barrier closer to the weather side of the wall.  The value of the vapor barrier used under the slab-on-grade constructed floor can be compromised, if water collects in a sand layer that was added on top of the vapor barrier and under the slab.

Can money be saved by having an engineering review of the plans and specifications for potential moisture intrusion prior to or during construction?
Yes. Most of the design professionals are dedicated to a wide variety of issues and are meeting many constraints to complete the design.  The construction contractor has a set of focused priorities to complete the job on-time and on-budget and to meet the plans and specifications.  An experienced engineer review of the plans and specifications from the view point of having investigated moisture intrusion as a result of failures can be very helpful.  The review comments not only on what is required, but also what is not required that can cause problems for the structure.  If feasible, it is also desirable to require the reviewing engineer to participate in initial construction inspections and/or testing of prototype installations.  A few thousand dollars invested in the moisture intrusion review, inspection and testing can provide cost savings to the contractor and owner in the millions of dollars range.

What is mould?
Mold or mould is a group of microscopic organisms belonging to the animal and plant kingdom known as Fungi.  Moulds are fungi, usually either zygomcetes or hyphomycetes, associated with the deterioration of food or manufactured goods of organic origin. Fungus is a plant like organism that has no chlorophyll and must absorb food through the cell wall.  Two major groups are yeasts and moulds with moulds spores germinating to produce filamentous growths and yeasts germinating to form solitary rounded growths http://www.doctorfungus.org/thefungi/index.htm

Why do you spell mold with a u (mould)? 
Mould is derived from the Norse mowlde, for fuzzy. Mold, on the other hand, is from the French molde, for shape or form.  www.doctorfungus.org

Are bacteria and moulds the same?
There are some similarities, but moulds are larger than bacteria and are often associated with filamentous development. No fungi grow well in the absence of organic food substances.  Bacteria can live on inorganic materials as well as organic.

How does Lead or Asbestos experience help to address mould problems?
Lead is an inorganic element while Asbestos is an inorganic mineral.  Both of these materials have been used extensively in building systems.  The health hazards for these two materials have been well studied and detailed governmental regulations exist at the federal and state levels to address the problems.  The sampling, analysis, corrective actions, and reporting are all clearly specified for investigator and contractors to follow.  Mould is not an element. Mould is not a mineral.  Mould is not well defined in terms of regulation or governmental programs.  Mould is potentially a living concern.  Lead and Asbestos can be remediated, or permanently removed or fixed.  Mould amplification can only be mitigated as it will return if the conditions are right.  Lead and Asbestos training in personal protection, isolation, and handling materials of concern can be helpful.  The mould  principal hazards (or lack thereof), the investigative methods, the mitigation methods, the proof of clearance are all based upon biological and engineering principles not needed for Lead or Asbestos work.

What is the difference between remediation, abatement and mitigation?
            Remediation: correcting an error
            Abatement: reducing the degree or intensity of, or eliminating
            Mitigation: measures taken to reduce adverse impacts on the environment

What causes mould to grow indoors?
Mould is found and in most if not all locations on Earth.  The Mir Space Station was even plagued with mold growing between the glass in the windows. Indoor moulds are outdoor moulds surviving indoors.  Moulds are able to survive from freezing to about 140°F.  To be overly simplistic, mould growth requires the viable spore + moisture (60% or more humidity or equivalent water activity level) + food (cellulose) + stagnant air (to avoid being blown away).  An indoor area does not “get mould” it has always had mould from the day it was constructed.  If the conditions indoors are right, the pre-existing mould indoors will amplify.

What is mould amplification?
From an engineering point of view mould amplification can be measured two ways:
 1) if the mould spores have germinated and the colonies have grown to the extent they are visible to the naked eye, the mould has amplified;
 2) as these are microscopic organisms they can be growing, but not be visible;   if the moulds are growing they are producing spores;  if the indoor airborne spore levels and types are significantly greater than the outdoor airborne spores = amplification.

What is a significant difference?
Mould levels vary during the day depending upon a wide variety of environmental conditions.  A given outdoor sampling location will produce not only different numbers of spores, but also different genera during a given time period.  From an engineering point of view and thousands of measurements taken, the outdoor level can easily change by a factor of 2 or 3 within a day.   HTA has data that demonstrates air data will fluctuate by a factor of 2 or 5 within minutes. In an extreme instance we had a fluctuation by a factor of 37 within 5 minutes.  From an action evaluation point of view, an indoor level that is an order of magnitude higher than outdoor is unusual.  A rationale can therefore be offered for agreement that between 3 and 10 times outdoor is reason for investigation or concern.  Until health risk standard are available, it may be prudent to split the difference (10-3)/2 + 3 use 6 or 7 times outdoor level as a threshold for significance.

Is the mould indoors a more toxic mould than that found outdoors?
Toxic is a loaded word that should not be used in this context.  Generally it can be a given that mould found indoors came from outdoors.  The term “ toxic” must be evaluated as:  1) what mould is found indoors; 2) what are the levels; 3) what is the duration of human exposure; 4) what is the frequency of exposure; and 5) what is the sensitivity of the individuals being exposed?  Without specific answers to each of the 5 questions above the term “toxic” is only speculative, at best.

What is the real problem with mould indoors?
Moulds present a nuisance of discolorations, odors, Moulds pose two major problems.  1) Over a very long period of time, with continued wetness, moulds can pose structural damage threats to buildings and contents.  2) Moulds are alleged to pose human health threats.

These reported human health threats must therefore be associated only with the occupied portion of the structure or a demonstrated pathway to the non-occupied portion of the structure.  From a disease point of view the CDC has indicated that there is evidence linking mould to allergies and asthma.  Other diseases and maladies are not well supported by medical findings and medical levels of concern are reported to be well above those that are often sited to justify expensive and inconvenient mitigation actions see http://www.acoem.org/guidelines.aspx?id=850  where medical professionals have produced evidence based statements showing the lack of clinical evidence of human health damage other than allergies, etc.

Are there real health effects from mould exposure to humans?
Yes.  From the research we have investigated the medical profession has determined that persons who are sensitive to moulds and are prone to allergies and asthma can be affected by elevated indoor levels of mold. The CDC has provided guidance in this area in the last few years http://www.cdc.gov/nceh/ehhe/about.htm  

In addition it has been dertermined that persons that are very young or very old or may have a compromised immune system are thought to be at a much higher risk than the rest of the normally healthy population.   Many of the other claims seen in the popular press and media are without clinical medical support and appear to involve circumstances and problems beyond mould amplification.

What is the “black toxic mould”
Typically people are referring to Stachybotrys chartarum, but there is also a black mould called Chaetomium.  A common blue – black mould is Ceratocystis Ophiostoma that is found on most lumber and this group is not known to be much of a human or animal health threat.  The term “toxic” is a misnomer for the reasons as given in the FAQ above.  There are many moulds that are black and may or may not produce mycotoxins.  There are many moulds that are not black and they too may or may not produce mycotoxins.  A mould genus that does contain species that can produce mycotoxins still needs the right substrate and food, the right environmental conditions, and to be at the growth stage to produce the mycotoxins.  Without a sensitive receptor present, without a defined exposure pathway, and without a viable growth of a mycotoxins producing mould (in the process of producing the mycotoxins) there can be no toxic mould, black or not.  Experts such as Harriet Burge have calculated and shown that it would take a very long time of  being exposed to a very large number of mycotoxins producing spores to accumulate even  1 nanogram of mycotoxins (if that were determined to be of significance).

In the area of mold investigations and mitigation, which of the many certification designations are issued by the government versus trade and professional organizations?
Registered Professional Engineers (PE) , Registered Environmental Assessors (REA), Certified Asbestos Consultant( CAC) are State government certifications issued upon education, completion of experience, and testing, but are not specific to mold.   The Business and Professional Code holds the PE to be responsible for the protection of health and welfare.

Certified Industrial Hygienist (CIH), Certified Environmental Investigator (CIE), Certified Mold Inspector (CMI), Certified Indoor Air Quality Manager (CIAQM), Certified Microbial Investigator (CMI), and many more are issued by trade and professional organizations and may require short courses, experience, or tests

Are there governmental statutes and regulations defining safe or hazardous levels of mould indoors?
Not in this country, however some states have been trying to come forward with rules.  Canada has tried and stopped with only general guides.  Ingestion of mouldy food has been addressed by government agencies.

Are there government standard tests for mould?
No.  There are only non-binding suggestions and guidelines that clearly place the responsibility upon the Environmental Engineer or other health professionals.  There are guidelines and textbooks that suggest methods as well as methods authored by equipment vendors.  Many investigators will talk about “industry standards”, however mold issues have too many unique variables and circumstances to have one “industry standard” to fit all cases.

Are there government standard qualifications for commercial mould investigators or mitigators?
No.  There are trade association and professional organizations offering guidelines and calling them standards for their members to qualify and to follow and suggesting that others also follow these methods.  Often investigators and mitigators using methods and training appropriate for Asbestos or Lead issues miss the significance of mould issues and tend to error in the direction of being overly conservative thereby driving up costs. 

Is removing and throwing away everything that may have come in contact with mould justified?
An over simplified answer is no.  However, it should be recalled that the mitigation actions should be designed upon the needs of the occupants and their known sensitivities.   An additional consideration is the cost of cleaning and testing.  Hard surfaced items can be readily cleaned and disinfected.  Many soft goods can be laundered or dry cleaned.  The paradox is that most soft goods could contain mould spores prior to any mould amplification within a building simply from the item manufacture, transport, storage or use and therefore the definition of “clean” is difficult, as there is often no background level known.  Due to costs of testing before and after cleaning and the costs of cleaning a judgment for cleaning versus disposal can be based upon the answer to the question. Can the item be replaced for $250 or less? It can be argued that almost anything can be cleaned and restored, but the costs involved require these techniques to be reserved for items the occupants highly value including items with emotional significance.

Why are physical mould removal methods often used rather than disinfection?
It would appear that many in the mould assessment and mitigation businesses are not trained, qualified, or comfortable using chemicals within buildings.  It is often stated by those limited to sanding and vacuuming or detergent cleaning of visible mould that the USEPA and the ACGIH prohibit the use of chemicals to address mold in buildings.  This is not true.  

The USEPA does not prohibit the use of chemicals, but rather points out the care that should be used in their application, especially those chemicals that are registered pesticides (www.epa.gov/iaq  Mold Remedieation in Schools and Commerical Buildings).   It is recommended that those who do not know how to use these chemicals safely should not use chemicals.  It is unfortunate that USEPA and OSHA have incorrectly lumped Sodium hypochlorite into the biocide category rather than into cleaning agents, as it is often sold.   (Is it wise to take such a strong stand that these agencies are wrong?) It should be recalled that the same USEPA requires public water supplies to be disinfected and the most popular form of disinfection is chlorine.  FEMA in responding to flood damage and addressing mould infested structures routinely directs and pays for cleanup activities that rely heavily upon the use of disinfectants such as Sodium hypochlorite.    The ACGIH (www.acgih.org   Bioaerosols Assessment and Control) has advised that use of biocides should be carefully considered before any application and that cleaning with a detergent or cleaning agent would provide the results that a biocide would provide without the added chemical hazards.  However, the ACGIH also adds a full Chapter #16 on the use of biocides and antimicrobial agents.  Unfortunately, Sodium hypochlorite is lumped into this “biocide” category.  It is reasonable for ACGIH to advise caution in the use of fungicides (normally designed for outdoor or uses other than mold amplification within buildings) as these are designed killers.  Sodium hypochlorite, on the other hand is not a specific poison, but rather an oxidizer that is commonly used in household cleaners, and to sanitize public facilities and swimming pools. Sodium hypochlorite is regulated by the USDOT and shipped as an oxidizer, not a biocide.  Contrary to the guidance provided, Sodium hypochlorite does not just kill mould and leave behind unaffected mycotoxins or other problems.  Sodium hypochlorite has been used since the days of Louis Pasture to disinfect surfaces, water and other items by oxidation.  HTA has viewed and video taped the (Sodium hypochlorite – mould) reaction under the microscope where the visible mould is treated with Sodium hypochlorite and within seconds to a few minutes the spores are attacked and disintegrated.  At the molecular level there can be reaction by-products as there are in potable water disinfection reactions, but the significance is the chemical oxidation has removed the mould totally.  The oxidation reaction driven to completion would produce CO2, water and ash.  The ability of the Sodium hypochlorite liquid to be introduced into hidden spaces and frame joints hosting mould is far superior to the conventional technique of sanding and vacuuming.  The saving using the disinfection processes are significant as there can be reduced time, reduced labor hours, and minimal destruction of building systems.  Labor is always the most expensive component to any remediation, mitigation or abatement job.

Consider: if one is really concerned about the infectious biological nature of mould within a building  - -  please recall:  when was the last time one saw or heard of a hospital dealing with the cleanup of an infectious biological agent using sanders and vacuums or completely demolishing the building!  Hospitals, since Louis Pasture’s discovery, have relied upon disinfection and often that is some form of an oxidizer such as chlorine or Sodium hypochlorite.  The broad spectrum oxidation reaction is not limited by mould or bacteria species and effectiveness of a specific poison on that species.  That is the well known and demonstrated principle of DISINFECTION.

Is mould testing required to understand and correct an indoor mold amplification problem?
Testing of surface or air borne mould is only needed if the situation is such that there is a human health concern within a building and there is need to demonstrate effectiveness of any corrective actions taken.  While corrective action may be taken without testing, some discolorations of building systems can be caused by actions other than mould (water stains, burns, construction marks, etc).  This can lead to an unjustified mitigation expense.  Without testing it is very difficult to define a cleanup goal or to demonstrate when the cleanup goal is reached.  Not all moulds present the same health concerns to all people.  Knowing the genera (ideally the species) of visible molds and the lack of sensitivity of the occupants to those molds could allow more cost effective and appropriate corrective actions to be taken.

What is a disinfectant?
Disinfectants have been used by medical and sanitary professionals for about 200 years.  Disinfection is not sterilization.  The most widely used and successful disinfectants are various oxidizers.  A disinfectant is not a poison, because the oxidation reaction is very fast compared to any metabolic reaction.  Chlorine is the most common and may be administered in several physical forms including vapor, liquid and solid.  Other oxidizers used include Hydrogen Peroxide, Bromine, Iodine, Potassium Permanganate, Ozone, and many more.  The principle of disinfection is to basically “wet combust” oxidize the offending organic particles (bacteria, mould, etc).  The completed oxidation reaction would take mould or other organics and produce Carbon dioxide, water and ash

Is there a difference between a biocide and a disinfectant?
Yes. However, some government agencies and professional organizations have generally categorized disinfectants into the biocide grouping. It should be understood that Biocides are not part of the Federal regulatory schemata under The Federal Insecticide, Fungicide, and Rodenticide Act.  Biocides are not recognized by the USDOT as a Hazardous Material classification for shipping chemicals.  Biocides do not appear to be regulated by OSHA, but the term appears to be used by OSHA in the withdrawn proposed Indoor Air Quality Regulation 29CFR 1910, 1915, 1926, 1928.  Those using the term biocide appear to be referring to any chemical that may be used in a mould or bacteria killing mechanism.  While this may be helpful to some, it would appear to confuse an already overburdened lexicon dealing with mould.  Disinfectants employed for the chemical removal of mould from building surfaces may be generally described as oxidizers as described above.

Once mitigated, will mould return and amplify?
Yes. Unless the conditions that caused the mould to amplify are corrected and maintained, the mould amplification (not necessarily the same genera) will be re-established.  If the source of moisture intrusion is not stopped and the area kept dry, and/ or ventilated, mould amplification can begin.  If there is residual mould, such as in crevices not reachable by sanding or vacuuming, and there is any stimulus by elevated moisture, the mould amplification will happen.  The mould spores are present. The building is made of cellulose (wood, paper) as the food source.  If the moisture level rises with ventilation decreases, mould amplification will happen.