Indoor Air Quality Solutions, IAQS

AIHA Position Statement on Mold and Dampness in the Built Environment – Florida Indoor Air Quality Solutions, IAQ

The approximately 10,000 members of the American Industrial Hygiene Association (AIHA) serve in the occupational and environmental health and safety profession, practicing industrial hygiene in industry, government, labor, academic institutions, and independent organizations, primarily in the United States and Canada. The AIHA is a cognizant authority on all aspects of the profession. AIHA Technical Committees endeavor to ensure that reliable information is provided to all those concerned with the health and safety of people in the workplace and, in some cases, homes.  AIHA members often play the unique role of working with other professionals, as risk managers and risk communicators, to solve problems and to protect the health and wellbeing of workers and the general public.

Since 1996, the AIHA has been a leader in the development of information and best practices on the management of mold and dampness problems in the build environment. This information has been relied upon by officials who develop and
enforce public policy on indoor environmental quality (IEQ) for the non-industrial workplace, including schools. AIHA has also provided accessible information for individuals to enable more informed choices. It is appropriate to make clear the
Association’s positions with respect to reducing the risks associated with indoor microbial growth, and to define and explain the role of AIHA members in such endeavors, to all parties.

MOLD & HEALTH
Modest wetting and drying in buildings and in ventilation systems is normal and generally poses little risk for occupant health. Similarly, very brief episodes of wetting are not usually a problem provided that steps are taken to rapidly dry all materials.(1) “Dampness” is the presence of unwanted and excessive moisture in buildings.(2) This can lead to the growth of mold, fungi, environmental bacteria, and, in homes, house dust mites.

The term “mold” is a colloquial term for a group of filamentous fungi that are common on food or wet materials. Most of these are Ascomycetes that produce a lot of spores. The molds that grow on damp building materials are normally found in the soil and are adapted to grow on a wide variety of materials. Outdoors, molds live in the soil, on plants, and on dead or decaying matter. There are thousands of species of mold and they can be any color. Different mold species are adapted to different moisture conditions, ranging from just damp to very wet. Many times, mold can be detected by a musty odor. Live spores act like seeds, forming new mold growths (colonies) under the right conditions.(3)

Well conducted epidemiology studies in several countries have consistently shown that exposures from building/house dampness and mold have been associated with increased risks for respiratory symptoms, asthma, hypersensitivity pneumonitis, rhinosinusitis, bronchitis, and respiratory infections.(4,5) In studies conducted in the nonindustrial
workplace, individuals with asthma or hypersensitivity pneumonitis were found to be at risk for progression to more severe disease if the relationship between illness and exposure to the damp building was not recognized and exposures continued.(6)

Three recent, high quality, systematic reviews of the available evidence concluded that the implementation of interventions that combine elimination of moisture intrusion and leaks and removal of moldy items help to reduce mold exposure and respiratory symptoms and new onset asthma.(4,5,7) This position has also been taken by National Institute for Occupational Safety and Health (NIOSH) and many State governments (8), Health Canada(9,10) and internationally by the World Health Organization(11).

Based on this evidence, the position of AIHA is that persistent dampness and mold damage in the non-industrial workplace, including schools and residential housing, requires prevention, management and effective remediation. If visible mold is present, it should be remediated, regardless of what species are present. Such actions are likely to reduce new onset asthma, lead to savings in health care costs, and improve public health.

Therefore
1. While the design and location of a building have the greatest impact on the onset of serious mold damage, maintenance and effective management of mold and dampness requires an ongoing strategy involving occupants, building owners and managers, ventilation experts and occupational hygiene professionals.(1,2)

Owners and occupants should take action to detect and correct leaks, condensation problems and floods as soon as they are discovered. The potential for building structural damage, microbial growth and increased adverse health effects can, and
should, be reduced by limiting the buildup of indoor moisture. A formal mold/water prevention program with clear actions and responsibilities is required for an effective response to signs of moisture.(12,13) The actions taken by all stakeholders, including designers, contractors, owners, and occupants of buildings, are critical to effective management of prolonged dampness in buildings. An effective prevention program is evidence of appropriate due diligence to protect both the health of occupants and visitors, and to preserve the building fabric. As new buildings are constructed, or older buildings are subject to major renovation, consistent effort is needed on the part of the architects and engineers involved in the design and construction of the structure, cladding, roof and HVAC system to make the building durable.(1,14)

2. It has long been recognized that, based on the application of existing methods to analyze air or dust samples, there are no quantitative, health-based microbial exposure guidelines or thresholds.(8,10) Sampling data that may be developed during an investigation must be comprehensive and communicated in a form useful to physicians and allied professionals, building occupants and decisionmakers.(15,16)

AIHA recognizes that there are a number of audiences for the reports that are provided pursuant to a mold investigation. Regardless of the nature of the client (homeowner, insurance agent, large property company, government), reports must provide information that can (a) be translated into an action plan for repair and rehabilitation of the space, (b) provide a basis for protecting occupants and remediation workers health and, in certain situations (c) be useful for the personal physician and/or public health officials.

Investigators should provide clear and consistent field notes with sufficient detail to allow the field work and sampling data, if any, to be interpreted, verified, and repeated. The report should include, at a minimum, appropriate documentation of sample handling and reporting results. Ideal documentation should be thorough, detailed, readable, and focused. Additionally, it should present sufficient information to allow the work to be verified and repeated, and it should describe all quality assurance procedures.(17,18)

AIHA recommends that clients verify that the consultant has suitable training and project experience, as well as appropriate and related references.(19) Almost all industrial hygienists (IHs) have college degrees in engineering or the natural sciences, such as biology, chemistry, biochemistry or microbiology. Additionally, 42% have master’s degrees, and 12% have doctoral degrees. Industrial hygienists also have specialized training in ventilation engineering, environmental health, toxicology and microbiology.

Unless this is waived by the client, investigators should be independent of the remediation contractor and testing laboratory associated with the project.(16,19,20) Basic competencies that should be assessed by clients include knowledge and education in exposure characterization, microbiological assessment and remediation, general knowledge of the ecology of fungi and bacteria associated with damp or flooded buildings, building science and problem areas in Heating Ventilation and Air-Conditioning systems.(19,20) If samples are collected, laboratory analytical staff should have specific training and experience in the identification of environmental mold and bacteria, and be able to demonstrate successful participation in an external proficiency testing program.(2,21) Some States have certification requirements and other regulations regarding mold-related activities or remediation. A number of Canadian municipalities have regulations that cover mold damage in residences from illegal marijuana grow operations.

Recent guidelines from the American Academy of Allergy Asthma and Immunology focus on factors that promote allergen and contaminant production (‘facilitating factors’, in this case moisture) and reservoirs.(15) In this context, properly conducted building inspections, which depend on the training and experience of the investigator(s), are essential to physician evaluation. Physicians reviewing such reports should find clearly described key elements and be able to judge the quality of a report. At a minimum, reports should include a statement of purpose and limitations, observations, results of any testing, conclusions, and recommendations. Such reports should not include any speculation or conclusions concerning medical causation.(2,16)

Since current analytical methods do not provide information on the health risks associated with mold exposures in the built environment(8,10), health assessment is primarily based on the nature and extent of the mold and water/moisture damage and the type of reservoirs present (e.g. carpets, soft furniture). In most studies and a recent meta-analysis on the subject, semi-quantitative estimates of the extent of visible mold/dampness has been identified as being the best predictor of long and short-term health outcomes.(5,9,22,23) The investigator’s report needs to present this information in a clear fashion according to methods discussed in the AIHA publication Recognition, Evaluation and Control of Indoor Mold (“The Green Book”).(2) Air and/or settled dust sampling can be used to defend hypotheses about the nature of the contamination, ‘hidden’ sources of contamination, and whether or not the indoor air is similar to outdoor air.(16,24)

3. Investigation and remediation of mold and moisture damage in buildings must be based on an informed inspection augmented by the judicious use of existing sampling methods, primarily for the purpose of detecting any hidden damage.(2,9) The protection of remediation workers and occupants during renovations is essential.(2,9) In case of occupants with more serious pre-existing respiratory conditions, relocation may be appropriate.(25,26)

If mold is suspected, but not visibly detected after a thorough inspection, then microbial air sampling conducted in accordance with guidance documents can be useful.(2,3,24) This sampling may reveal evidence of indoor mold amplification or reservoirs,
particularly of mold that is considered “hidden” behind walls and other building structures. If mold is being removed and there is a question about how far the colonization extends, then surface or bulk sampling, in combination with moisture measurements from affected building materials, may be useful. Sampling for airborne mold spores can indicate whether the mix of indoor molds is “typical” of the outdoor mix or, conversely, “atypical” or unusual at the time of sampling.

Any mold sampling that does occur must be performed by qualified and experienced investigators familiar with current guidelines and, if applicable, local regulations. Samples should not be taken without a clear purpose (i.e., testing a hypothesis) and a sufficient number of samples must be taken to reliably assess the existing conditions. Laboratories vary in experience and proficiency; using an AIHA-LAP, LLC EMLA Paccredited lab or ISO 17025 equivalent is recommended.(3)

4. It is not unusual for buildings to have a number of concurrent problems that affect IEQ or the perception of IEQ. Water and moisture damage can result in the release of gasses from some building materials.(8) Investigations of apparent or suspected mold-related health complaints must consider all possibilities. While mold damage comprises a large percentage of problem situations, studies of occupant complaints find that a high percentage have an outdoor air make up below the American Society for Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) standard, inappropriate and inadequate temperature and
humidity levels, inadequate control of contaminants from outdoor air (including ozone, traffic pollutants, etc.), contaminants arising from equipment or activities within the building or house (including cooking activities), and poor air distribution.(22,27,28)

IHs and other IEQ practitioners should approach mold, water intrusion, and IEQ investigations with the same mindset they use when they approach all investigations. The process includes three of the five key industrial hygiene elements: anticipation, recognition, and evaluation. While the IH can reasonably anticipate that there will be mold exposures associated with water intrusion, mold may or may not be the primary cause of any health effect(s) that may be experienced by the occupants. The IH should ensure that, while investigating mold-related complaints, whether apparent or reported, active consideration of other possibilities affecting IEQ in the space is an essential part of the investigation.(29)

In addition to mold-related exposures, contaminants that are both directly and indirectly associated with water-related damages may also be affecting the occupants. These contaminants may include, but are not limited to:

• particulate and gas/vapor contaminants associated with improper combustion ventilation or improperly operating utilities, such as carbon monoxide, nitrogen and sulfur compounds, soot and other fine particles, fuel and other volatile organic compounds (VOCs), etc.;
• VOCs from construction product degradation and/or off gassing, such as formaldehyde and other aldehydes, phenolics, and amines;
• organisms that proliferate under damp conditions or when maintenance is substandard, such as bacteria, amoeba, dust mites, cockroaches, and rodents; and,
• animal and chemical-based allergens already present and/or exacerbated by the water damage.

Many potential contaminants may be present along with mold damage that can affect health or the safety of investigators, remediation workers, and occupants. For example, failure to recognize the presence of asbestos, radon, or lead-based paint could lead to their disturbance during investigative or remedial activities, unnecessarily creating a new hazard. Finally, there is a need to recognize the potential hazards associated with remedial alternatives that may lead to the introduction of pesticides, ozone, chlorine dioxide, and other chemicals that could exacerbate existing health conditions or lead to new health issues.

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Florida Meth Lab – Florida Indoor Air Quality Solutions, IAQ

By SHELDON GARDNER
Sunday, April 7, 2013

Methamphetamine use is growing across Florida, and that trend is reflected in St. Johns County where the number of meth busts has increased for the past few years.
 
St. Johns County’s first meth bust came in the 1970s, and meth labs weren’t discovered regularly again until the early 2000s, according to previous stories.
 
Deputies started finding a few meth labs a year in 2008, said St. Johns County Sheriff’s Cpl. Mike Hartsell. In 2011 and 2012, the Sheriff’s Office found more than three dozen meth labs.
 
“It’s not gonna slow down,” Hartsell said.
 
Meth labs have been found across the county in hotel rooms, homes, backpacks and cars. Many of them are clustered in and around the city limits, but labs have also been found in Hastings, Elkton, Ponte Vedra Beach and off County Road 210 and 208, according to Sheriff’s Office records.
 
Most of them are small-scale, one pot labs, that are highly mobile and produce enough meth for personal use.
 
The same is true statewide. Most labs fit in a Gatorade bottle, small enough so that someone could “start making meth in one county and drive through three counties before it’s done,” said David Gross, special agent supervisor with the Florida Department of Law Enforcement, which monitors trends in drug use.
 
The increase in meth lab discoveries is also happening across the state, but meth is already a nationwide problem, Gross said. Meth has been in Florida since the late 80s or early 90s, but use and production started to pick up in 2008.
 
In 2008, law enforcement agencies across the state reported 180 meth labs, Gross said. That number rose steadily. In 2011, 676 meth labs were found. There were probably more since multiple areas in the state did not file reports. Reporting is on a voluntary basis.
 
In 2012, 930 meth labs were reported statewide.
 
In May 2011, the St. Johns County Sheriff’s Office Clandestine Laboratory Enforcement Team formed to better respond to the growing problem. The team is made up of deputies trained in handling meth labs. Hartsell supervises one of those teams.
 
When the Sheriff’s Office meth team arrives at a scene, officials suit up and remove the lab from the home. That takes four to six hours and costs from $500 to $2,000 depending on the size of the lab, Hartsell said.
 
Meth cooks endanger not only the people cooking them, but surrounding communities. The gases used in the cook are toxic and highly flammable and explosive. In 2010, a Sheriff’s deputy had to be taken to the hospital for an inhalation injury after breathing in the toxic fumes during an investigation, Hartsell said.
 
Meth use also increases criminal activity, affects surrounding communities and costs the county money. As with other drugs, people often steal to support their habit, Hartsell said.
 
Meth labs are toxic to people and homes.
 
Cooking meth or smoking it creates gases that seep into walls, carpets and furniture, he said. If a building is not cleaned properly, the residual gases are still there, and it’s a health risk.
 
Depending on the extent of meth use, decontaminating a building could mean ripping out walls and throwing away furniture, costing thousands to tens of thousands of dollars. Sometimes houses are so badly contaminated that they need to be demolished.
 
St. Johns County Code Enforcement officials recently demolished a mobile home at 1990 Powell Road because meth had been cooked in the home. Two labs had been found there over the past few years. The property owner opted to have the building torn down instead of paying for the clean-up.
 
Officials said meth use will continue to be a problem in the state and the county despite efforts to fight its spread.
 
“Right now that’s the future of narcotics in our county,” Hartsell said. “At least for the time being.”
 
■
 
A few facts about meth
 
Methamphetamine facts from the Drug Enforcement Administration:
 
Street names: Batu, Bikers Coffee, Black Beauties, Chalk, Chicken Feed, Crank, Crystal, Glass, Go-Fast, Hiropon, Ice, Meth, Methlies Quick, Poor Man’s Cocaine, Shabu, Shards, Speed, Stove Top, Tina, Trash, Tweak, Uppers, Ventana, Vidrio, Yaba and Yellow BamLooks.
 
■ How it’s done: Meth can be swallowed, snorted, injected or smoked.
 
■ Affects: Meth creates an intense rush with highs that can last for half a day. The drug releases high levels of dompamine into the pleasure areas of the brain. Long-term abuse can cause addiction, violence, anxiety, confusion, insomnia, paranoia, hallucinations, delusions. Dopamine-producing brain cells and serotonin-containing nerve cells can be damaged by exposure to meth.
 
■ Overdose: Taking too much meth can cause a heart attack, stroke and multiple organ problems as the body temperature is raised to dangerous levels. Overdosing also can cause convulsions.
 
■ Legal: Meth is a Schedule II controlled substance and is prescribed, in very limited use, to treat obesity and attention deficit hyperactivity disorder.
 
■ Where it all started: Mexico produces most of the meth that is imported into cities in the US. Many meth labs found in the U.S. are small scale labs.
 
■ What’s been done: The Combat Methamphetamine Epidemic Act of 2005 requires businesses that sell non-prescription products that contain major ingredients in meth — pseudoephedrine, ephedrine or phenylpropanolamine — to make customers show ID and sign a logbook to purchase the products. They must also keep the products in a locked cabinet.
 
■ Florida has its own laws regarding the sale and purchase of ephedrine and its related compounds. The State Legislature passed a law in 2010 that controls the sale and purchase of the chemical, and created an electronic database for sellers and law enforcement to keep track of who is buying and selling, according to the Florida Department of Law Enforcement.

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Florida Indoor Air Quality Humidity & IAQ

Maintaining relative humidity below 50% inhibits mold and mildew growth, dust mite infestations, and bacteria. This lower relative humidity also reduces the out-gassing of volatile organic compounds (VOC’s). Molds are incapable of obtaining the moisture needed for their development directly from the atmosphere, but they can obtain it from a substrate, which has absorbed moisture from moist air (60% to 100% relative humidity).

The relative humidity of the air has an indirect effect on fungal growth, and the more hygroscopic a material is, the more susceptible it is to mold growth. The minimum moisture content at which mold growth occurs depends on the material and usually ranges from 10% to 14%. Suitable substrates include carpet fibers, gypsum, concrete, bricks, etc.
Mold spores are everywhere all the time, entering from outdoor air as well as on pets and clothing. A mold spore landing on an indoor surface is likely to be insignificant and amount to little more than a common component of indoor dust, until such a mold spore lands on a moist organic surface (such as drywall.) High indoor humidity causes the surface moisture level to be sufficient for mold sporulation.  Since a mold spore requires moisture to propagate and grow, the indoor humidity level is a key gating factor in the control of indoor mold (and dust mites) in buildings.
Certain common mold genera and species, such as some members of the Aspergillus sp. and others grow readily on common building materials if they also have enough moisture. While there are fungal species that are able to grow under a remarkably wide range of environmental conditions, keeping indoor humidity at the appropriate level will reduce the chances of growth of the most common indoor problem molds.
High indoor humidity can encourage more issues than indoor mold. The same moisture conditions that support growth of problematic indoor molds also encourage the development of bacterial hazards, dust mite populations, mite fecal allergen problem, and possibly other insect problems in buildings.
The same measures of humidity control to prevent mold growth are needed to discourage the dust mite population that exists in all living areas. Measures discussed in this article including choosing and maintaining the proper humidity level to avoid indoor mold will also work to minimize the level of dust mites and dust mite allergens.
Keep the indoor humidity level in the mid-comfort range. A maximum indoor relative humidity of 50% RH may be acceptable, 45% RH better. At 60% indoor RH, we’re entering the indoor mold-formation risk zone of high interior moisture in building wall or ceiling cavities or on wall and floor surfaces, possibly conducive to mold growth.

John Lapotaire

Florida Indoor Air Quality Solutions

www.FloridaIAQ.com

Particle pollution, also called particulate matter or PM, is a complex mixture of extremely small particles and liquid droplets in the air. When breathed in, these particles can reach the deepest regions of the lungs.  Exposure to particle pollution is linked to a variety of significant health problems such as asthma.

Particulates are a mixture of organic and inorganic substances suspended in the air. They can be solids and/or liquids and exist in a range of sizes. Particulate size is measured in micrometers (µm), one millionth of a meter. The EPA refers to different groups of particulates that include:

1. Total suspended particulates (TSP) – representing the range of particulate matter normally found in the urban atmosphere. TSP generally includes from 1µm to 50µm.
2. PM₁₀ – refers to particulate matter of less than 10m m in diameter. PM₁₀ is generally considered the most useful particulate measure. Particles less than 10µm in diameter can be inhaled and have the potential to reach the tracheo-bronchial region of the lung.
3. PM_2.5 – comprises of fine particulate matter less than 2.5µm in diameter. Particles of this size are capable of deep lung penetration.
4. Total suspended particulates (TSP) – representing the range of particulate matter normally found in the urban atmosphere. TSP generally includes from 1µm to 50µm.

The Occupational Safety and Health Administration have a recommendation for 8 hour exposure for particles in the .3 µm size which is a recommended 0-40,000 particles/cc this is found in the OSHA Technical Manual.

Particulate Reduction;

The goal of improving the Indoor Air Quality is going to begin with particulate reduction.  Particulate matter (PM) is the name for a wide range of particles that are small enough to be carried by the air, therefore; breathed in by people. They can be solid or liquid, or a mixture of both.

The size of particles may range from 0.005 µm to 100 µm in diameter. In comparison, the average size of a human hair is 60 µm. PM₁₀ are particles that are 10 µm or less in diameter.  PM_2.5 are particles of 2.5 µm or less in diameter.  The finer particles pose the greatest threat to human health because they can travel deepest into the lungs.

Indoor particulate matter is a mixture of substances like these:

• Carbon (soot) emitted by combustion sources;
• Tiny liquid or solid particles in aerosols;
• Fungal spores;
• Pollen; and
• A toxin present in bacteria (endotoxin).

In a properly-maintained home, most of the airborne particulate matter comes from the outside. However, some homes do have significant sources of indoor particulate matter which come from the following sources:

• Cigarette smoking is the greatest single source of particulate matter in homes and buildings where people smoke;
• Cooking: especially frying and sautéing;
• Malfunctioning combustion appliances: for example, furnaces without a proper air filter;
• Non-vented combustion appliances like gas stoves;
• Wood-burning appliances like wood stoves and fireplaces: especially if the smoke leaks or back drafts into the home; and
• Mold growth.

Reducing concentrations of particulate matter in your home;

1. Furnaces and ventilation systems: Make sure that furnaces and ventilation systems are properly maintained, and that you replace filter screens as often as recommended by the manufacturer. All combustion appliances, including furnaces, should be inspected by a qualified technician yearly.
2. Cooking: Turn your exhaust fan on when you are cooking, and especially when frying.
3. Woodstoves: Choose properly sized woodstoves and make sure that the doors close tightly. Have your chimney cleaned yearly, too.
4. Mold: Prevent mold growth and the release of mould spores into your indoor air by controlling humidity and fixing water leaks and water-damaged areas
5. Smoking: Don’t allow people to smoke indoors because particulate matter levels increase with every smoker in the building.
6. Clean: Use your HEPA vacuum cleaner regularly.

Your vacuum cleaner, as a general rule, is really only efficient at trapping particles that have settled onto the floor or whatever surface you’re vacuuming.  Even many room air cleaners are of limited effectiveness in typical building environments, because every time someone walks across a room, opens a door or window, or flips on the central air handling home, thousands if not millions of superfine particles are introduced into the breathing space as the room air is disturbed or exchanged. Since portable air cleaner airflow rates are often fairly low in relation to the rate of room contamination, many people with portable air cleaners may still end up breathing more dust than they realize.

How can you stop or prevent dust? Well, you can’t, at least not completely, since even humans produce their own organic dust and the surfaces within the building are also constantly “shedding” micro-particles. Of course, you can make sure you have good entrance matting in place, so outdoor contaminants and dusts are not tracked in as much.  You can also try to cleanup or contain other sources of fine particles (e.g., paper dust from tissue boxes, dirty air ducts or HVAC filters, etc.) Finally, you can make sure that the processes you use to clean your homes removes rather than redistribute dust as much as possible. This would include vacuuming surfaces with an HEPA (high efficiency particulate air) filtered vacuum cleaner.   Use HEPA vacuum cleaners or high efficiency vacuum cleaner bags. These dramatically reduced the amount of dust, allergen and pollens pumped back into the air by the vacuum cleaner.

Florida Humidity Bloom Florida Indoor Air Quality Solutions IAQS

A humidity bloom is the growth of mold within a living space due to the elevation of indoor relative humidity at or above 60 percent relative humidity for a period of time greater than 72 hours and must be maintained for growth to continue.  When the humidity is above 60 percent relative humidity, molds will germinate causing what is referred to as a mold bloom.   These molds can bloom in many colors and are often confused with dust, dirt, foxing, or cobwebs.

Humidity for an extended period of time, typically in excess of 72 hours to initiate the bloom and must be maintained for growth to continue.  When the humidity is above 60 percent relative humidity, molds will germinate causing what is referred to as a mold bloom.   These molds can bloom in many colors and are often confused with dust, dirt, foxing, ghosting, or cobwebs.

Both active and inactive mold can have a distinctive smell, which most people describe as musty.

• Active mold in the early stages of a bloom has hair-like filaments in webs, which develop a more bushy appearance as the bloom matures. This is more easily seen under magnification. Active mold is soft and may smear when touched with a fine brush. It may also be slimy and damp.
• Inactive mold is dry and powdery and will seem to brush off materials readily.

Mold and mildew are words that refer to more than 100,000 species of fungi. Mold spores are present everywhere in our environment, generally in a dormant state where they do little damage. Spores require moisture to become active. They do not require light.

When water or high relative humidity provides the necessary moisture, dormant spores will germinate, grow fine web-like structures, and eventually produce fruiting bodies that release more spores. Most molds will germinate at 60 percent relative humidity. Increases in temperature can speed the growth rate of active mold.

There are 4 critical requirements for mold growth – available mold spores, available mold food, appropriate temperatures and considerable moisture. The removal of any one of these items will prohibit mold growth.

The only way to reduce the threat of mold in a home is to maintain an environment that is not hospitable for the germination of mold spores. The temperature should be 74-78 degrees F, and the relative humidity of 60% or less. It is important that the air conditioning system (HVAC) be kept on 24 hours a day, 7 days a week. Inconsistent operation or fluctuations in the temperature and humidity are the cause of many serious mold outbreaks.

Humidity

Humidity is simply vaporized water in the air. Your breath contains hundreds of droplets of invisible water vapor. You can see them when you breathe on a pair of cold glasses.

The term most often used to define the amount of water vapor in the air is “relative humidity.” Relative humidity is the percentage of water vapor in the air at a specific temperature, compared to the amount of water vapor the air is capable of holding at that temperature. Warm air holds more water vapor than cold air. When air at a certain temperature contains all the water vapor it can hold at that temperature, its relative humidity is 100 percent. If it contains only half the water vapor it is capable of holding at that temperature, the relative humidity is 50 percent.

If the outside air temperature in winter is 0°F and the relative humidity is 75 percent, that same air inside your 70°F home will have a four percent relative humidity. The Sahara Desert has an average relative humidity of 25 percent.

When air is saturated with water vapor, it has reached the dew point; at this point, water vapor condenses and produces visible water or “condensation.” In winter it usually occurs first on windows. When warm, moist air comes in contact with a cold window, air temperature drops and it can no longer hold the water vapor; condensation results.

Desirable Humidity Levels

The human body is comfortable when relative humidity ranges between 20 and 60 percent. In your home, an average relative humidity of 35 to 40 percent is appropriate when the outside temperature is 20°F or above. However, during cold weather, higher humidity ranges may cause structural damage because of condensation on windows and on the inside of exterior walls. As outdoor temperatures fall, condensation problems inside may develop.

The construction of a home also influences how much humidity is desirable. Tightly constructed buildings with properly installed vapor barriers and tight fitting doors and windows retain more heat and moisture. This is where mechanical ventilation becomes important. If a home does not have the proper mechanical ventilation, excess water vapor can move through walls and ceilings, causing wet insulation, peeling paint, and mold on walls and woodwork.

The following table shows recommended indoor humidity levels in relation to outdoor temperatures.

Maintaining relative humidity below 50% inhibits mold and mildew growth, dust mite infestations, and bacteria. This lower relative humidity also reduces the out-gassing of volatile organic compounds (VOC’s). Molds are incapable of obtaining the moisture needed for their development directly from the atmosphere, but they can obtain it from a substrate, which has absorbed moisture from moist air (60% to 100% relative humidity). The relative humidity of the air has an indirect effect on fungal growth, and the more hygroscopic a material is, the more susceptible it is to mold growth. The minimum moisture content at which mold growth occurs depends on the material and usually ranges from 10% to 14%. Suitable substrates include carpet fibers, gypsum, concrete, bricks, etc.

Mold spores are everywhere all the time, entering from outdoor air as well as on pets and clothing. A mold spore landing on an indoor surface is likely to be insignificant and amount to little more than a common component of indoor dust, until such a mold spore lands on a moist organic surface (such as drywall.) High indoor humidity causes the surface moisture level to be sufficient for mold sporulation.  Since a mold spore requires moisture to propagate and grow, the indoor humidity level is a key gating factor in the control of indoor mold (and dust mites) in buildings.

Certain common mold genera and species, such as some members of the Aspergillus sp. and others grow readily on common building materials if they also have enough moisture. While there are fungal species that are able to grow under a remarkably wide range of environmental conditions, keeping indoor humidity at the appropriate level will reduce the chances of growth of the most common indoor problem molds.

High indoor humidity can encourage more issues than indoor mold. The same moisture conditions that support growth of problematic indoor molds also encourage the development of bacterial hazards, dust mite populations, mite fecal allergen problem, and possibly other insect problems in buildings.

The same measures of humidity control to prevent mold growth are needed to discourage the dust mite population that exists in all living areas. Measures including choosing and maintaining the proper humidity level to avoid indoor mold will also work to minimize the level of dust mites and dust mite allergens.

Keep the indoor humidity level in the mid-comfort range. A maximum indoor relative humidity of 50% RH may be acceptable, 45% RH better. At 60% indoor RH, we’re entering the indoor mold-formation risk zone of high interior moisture in building wall or ceiling cavities or on wall and floor surfaces, possibly conducive to mold growth.

John Lapotaire, CIEC

Indoor Air Quality Solutions, IAQS

http://www.FloridaIAQ.com