Happy Thanksgiving from ThermaPure®. We are grateful for all the support this year.
Our thoughts and prayers are with the victims of the recent fires and their communities. We hope you will find this information on smoke remediation useful when the time is appropriate.
Wildfires – Overview
Extreme heat occurring across much of the western United States following a winter of significantly increased rain and snowfall creating the perfect condition for increased numbers, size and duration of wildfires. News sources have indicated that the wildland fire season of 2017 may yet be the worst fire season in recent history. This fire season is significant for the number of wildfires and the associated harm to an increasing number of humans living and recreating in wooded areas, as well as to many wildlife, timbers and structures. Whole communities have been severely impacted.
In a 2013 Senate Committee hearing, Thomas Tidwell, head of the U.S. Forest Service, testified before a committee on energy and natural resources that the fire season now lasts two months longer and destroys twice as much land as it did four decades ago. Fires now, he said, burn the same amount of land much faster. This year’s fire season may even exceed the trend Tidwell noted in 2013. Through July 9, 2017, California alone has experienced 2940 fires and over 68,000 acres burned. This is a torrid 28% increase over last year. More significantly, the accompanying number of acres burned has more than doubled.
Health Effects
With this increased potential of wildland fires, health concerns for certain individuals raise significantly. Forest fire smoke is made up of small particles, gases and water vapor. Water vapor actually constitutes the majority of smoke. However, what remains is significant in terms of health effects. The remainder includes carbon monoxide, carbon dioxide, nitrogen oxide, irritant volatile organic compounds (VOCs), air toxics and fine particles. Although smoke can be harmful to all individuals, it may be dangerous to certain populations, especially those already at risk for heart and lung diseases. Individuals with congestive heart failure, COPD, emphysema or asthma are at greater risk. Additionally, children and the elderly are more susceptible to harm from smoke.
Wildwood fires that occur in more populated areas, such as the 2013 occurrence of the Black Forest fire in Colorado, have increased health concerns when structural components become fuel. When structural fires are a part of the wildfire, the types of fuel increase and include all of the building materials – paint, carpet, floor coverings, wall coverings, insulation, manufactured materials, plastics, electronics, furniture, clothing, etc. Chemicals, such as pesticides, cleaning agents, and aerosols also become fuels. Many of these household chemicals are known carcinogens. Others can be damaging to structural components because of their corrosive nature. All of these are the effects from what we refer to as “smoke”.
Smoke Contamination in Structures
Particles are classified by their size. In a wildfire, hundreds of thousands of tons of respirable particulate matter is released. The vast majority of this particulate is smaller than 0.3 micron. To get a sense of size, a human hair will range from 30 to 120 microns. Because of the small size of this particulate, it is easy to see how smoke will infiltrate your house, even though you may have had doors and windows tightly sealed. Smoke damage is a common occurrence in structures near wildland fires. Generally, what we notice after a nearby wildfire is the presence of “soot” and the odor of smoke. Soot, or carbon black, is a relatively small component of the complex elements of smoke; however, it is the most easily recognized or observed.
It is difficult to assess the level of smoke contamination in a structure. Certainly there are tests that can be conducted. One such test is ASTM D6602-03b test method “Standard Practice for Sampling and Testing of Possible Carbon Black Fugitive Emissions or Other Environmental Particulate”. This method requires a wipe sample and a specific analytic protocol. It will provide you with an assessment of the presence of both char material and carbon black in particle sizes of 1 micron and larger. Other tests may be used to determine the presence of specific chemicals. All of these tests are complex and must be determined and conducted by a qualified consultant. If it is necessary to determine and quantify the presence of smoke contamination, a qualified environmental professional should be used.
Smoke Odors in Structures
Practically, contamination will be determined by odor. The presence of smoke in the structure will provide a recognizable odor. Odor brings awareness to the human olfactory system of the presence of airborne chemicals. Awareness of odors can also be from stimulus, triggering unwanted irritation to eyes, nose, and throat.
Smoke can affect anyone, not just those at increased health risk. “The odors from smoke can leave you feeling nauseous or with headaches, as well as an overall sense of annoyance at the constant smoke irritation,” said Janie Harris, Texas AgriLife Extension Service housing and environment specialist. “The smoke infiltrates homes and the lingering odor persists.”
Harris said the odor persists, even after a good scrubbing, due to tiny microscopic particles that cling to walls, furniture, floors and clothing inside the home. “Removing the smell of smoke can be a difficult job involving time, effort and money,” she said.
Odor Remediation
The most effective way to eliminate odor is to remove the source. Other methods are often attempted, such as masking the odor or altering it to a less offensive chemical, but source removal is the preferred method.
The Federal Emergency Management Agency (FEMA) provides wildfire smoke remediation guidelines in a pamphlet titled “Tips from State and FEMA on Smoke Removal and Fire Cleanup”. This guideline provides some tips on steps that should be taken. Their course of action includes the following:
- Pressure wash, scrub or disinfect all exterior surfaces including walls, walks, drives, decks, window and deck screens, etc.
- Wash and disinfect all interior walls and hard surfaces with mild soap or other appropriate cleaning solutions or products, and rinse thoroughly. Don’t forget inside cabinets, drawers and closets.
- Launder or dry clean all clothing.
- Wash, dust or otherwise clean all household items, including knick-knacks.
- Disinfect and deodorize all carpets, window coverings, upholstered furniture and mattresses with steam or other appropriate equipment.
Following these tips will most likely reduce the surface particulate to acceptable levels. However, it may not reach all areas and it may not eliminate the odor.
Structural Pasteurization as Odor Remediation
The process of structural pasteurization can be used to finish the job and have odor reduced or even eliminated. Structural pasteurization, a process used by ThermaPure® licensees, increases the temperature of a structure with the goal of reducing a targeted chemical(s) or organism to an acceptable level. This technology has been used for chemical reduction processes as well as in mold remediation, bacterial disinfection, and pest eradication.
With regard to chemical reduction, the temperature in the structure is elevated to 105ᴼ-120ᴼF, increasing the vapor pressure of the various volatile chemicals to speed up the process of off gassing. This temperature will be maintained for varying periods of time, from hours to a few days, depending on the complexity and severity of the smoke odor. A ThermaPureHeat® application is an engineered process; which typically includes air filtration, temperature control and monitoring, and air pressure control which will provide appropriate air and temperature distribution to the structure. This allows a more rapid off-gassing of chemicals while maximizing protection to the structural components and furnishings. Air filtration will use HEPA filters to capture much of the particulate and may use carbon filters to capture vapors. In many situations the structure, or portions of the structure, may be heated under negative pressure, allowing both ultrafine and fine particulate to be exhausted along with the target vapors.
Case Study – Fire in Structure with Smoke Damage Throughout
The case study project is a high-end, multi-story single family residential structure. The exterior consists of stucco/plaster over wood framing. The interior walls and ceilings are constructed of gypsum drywall and/or thin coat plaster over wood framing. The flooring is a combination of carpet, tile and wooden materials. The residence is located on a hillside with beach access in Malibu, CA.
The garage and primary entry is located at street level. The residence is approximately six stories from the entry area to the beach. The residence has approximately five levels which would be considered livable floors. The fire loss occurred in the kitchen of the residence. This area is located on the third level from the beach.
The insurance adjuster retained the services of Environmental Testing Associates (ETA), a southern California environmental consulting firm, to provide fire damage assessment and recommendations. The purpose of the requested work was to determine the amount of char material and/or ash/fugitive dust, if any, that may have contaminated the subject property and to gather information necessary to assist in the planned services necessary for the successful cleaning and restoration following the loss. This information would be used in conjunction with the accepted standards of care for treating, cleaning and the decontamination of the impacted areas.
ETA concluded that several areas had been contaminated by char materials and remediation/cleaning was necessary. Smoke-like odors were also noted within the subject property on all floors.
ETA’s recommendations were specific to each floor and included cleaning, removal of materials that could not be cleaned, and removal of loose items and either cleaning or replacement. An all encompassing recommendation was the use of filtration. Here are ETA’s filtration recommendations:
All areas of the residence: HEPA filtered air filtration units should be equipped with charcoal filters. Equipment should be placed generously throughout the residence and must be allowed to run during the entire restoration process. The filters within these units should be frequently/aggressively replaced.
A local restoration company was used to provide the cleaning restoration services. Once cleaning was completed, there was still a significant smoke odor remaining. The homeowner’s wife was chemically sensitive and although low VOC cleaning compounds had been used, there was still a concern that any additional use of chemical cleaners may not be effective and also may be harmful to the client. ETA recommended the use of a non-chemical remediation process, ThermaPureHeat® to complete the off-gassing of smoke-related chemicals and reduce or eliminate the odor.
A southern California based ThermaPure® licensee, was retained to provide the heat services. Because of the magnitude of the smoke odor and the size and complexity of the structure, it was determined that the target temperature would be between 110ᴼF and 120ᴼF for a duration of 10 to 15 days. Multiple types of heating equipment were used, dependent on access, ingress, size and complexity of the area. Electric heaters were used in some areas, hydronic heaters with heat exchangers were used on several floors and some direct-fired propane heaters were used nearer to ground level. In addition to heaters, fans and negative air machines (HEPA), moisture was introduced to the ambient air to reduce the potential damage effect of long term drying. The air exchanges were significant with approximately 3000 cubic feet of air per minute (CFM) exhausted. Particulate that had not been accessible to hand cleaning was aerosolized and either captured by the HEPA/carbon filtration or exhausted along with the bulk of the chemical vapor.
It is extremely difficult to eliminate smoke odor, but on the final walk through the client indicated that he did not detect any odor. This was a very successful smoke odor reduction project. Client and adjuster were extremely satisfied with the outcome. The alternative to this process would have been the expensive removal of many high priced decorative and structural elements and additional chemical application.
ThermaPure, Inc.
July 10, 2017
One advantage of ThermaPureHeat® is that it can treat multiple symptoms with one treatment, leaving you with a healthy home in no time!
We are excited to announce a new online learning center!
thermapureprofessionals.com
Decades of information, now at your finger tips. Brush up on important information you may have forgotten. Licensees and their employees may take the online refresher course for $300.00
The first 10 people sign up for beta testing will get to take the ThermaPure Level 1 course for FREE
(current licensees and their employees only)
Call our office (800-366-2022) today to sign up.
Best wishes,
Stefany Hedman
Chatting with ThermaPure. In this video we meet with Rich Grey of the Indoor Air Quality Consortium. In this video Rich discusses structural pasteurization.
Chatting with ThermaPure. In this video, Larry Chase explains why he believes ThermaPureHeat is the “Gold Standard” for certain remediations.
Watch this video which outlines a study that studied the chemicals that make up dust in our homes.
Please watch our Video which outlines the potential hazards that come from heat treating homes without filtration.
- Termite
- Flood
- BedBug
https://www.floodsmart.gov/floodsmart/pdfs/Spring%20Flood%20Risk%20Fact%20Sheet_FINAL_revised.pdf
http://www.pctonline.com/article/bed-bug-seasonal-study/
https://www.freshfromflorida.com/content/download/3145/19791/p01742_consumerinfo_drywood_0910.pdf
The beginning of the year is a time to plan for the upcoming year. One thing that is never planned for is a disaster. While disasters are usually sudden and unexpected, having a plan is the best way to prepare for the worst.
The above graph outlines the relative activity and danger that Termites, Bedbugs, Floods pose to your homes and families.
Floods are prevalent across the country as heavy rain and snowfalls saturate the ground in the winter. Then, when the snow melts, and continued spring rains fall, the ground can’t hold anymore water and floods are caused. Flash floods are also a danger, especially in drought prone areas that have sudden heavy downpours.
Termites pose a threat to your house almost all year round. Subterranean termites are active mostly during summer because the ground is softer and easier for them to burrow into your homes. However,they can be active all year round in temperate places that don’t get too cold. Another major type of termite is the drywood termite. These termites breed and live primarily inside houses and only leave to start new colonies. Because they aren’t affected as much by the outside weather they are active all year but swarmers are most commonly seen during the summer months.
Bedbugs are another pest that pose problems, not so much to your houses but to families and health. Bedbugs become more active in warmer climates. Bedbugs can also travel anywhere on clothing or in luggage. That is why the season for bedbugs is during peak travel months.
We hope this information helps you plan for your home maintenance in the upcoming years. If you need help taking care of any of these problems, using clean, pure heat visit our website www.thermapure.com or call our office at 805 641 9333.
By: Michael Geyer, PE, CIH, CSP
Heating structures, or areas within structures, is fast becoming the most effective method for bed bug eradication. Active structural heating relies on aggressive air mixing in order to be effective. However, aggressive air mixing generates significant, potentially harmful, aerosols of particulate matter. Methods exist to control the aerosols and they should be judiciously implemented when using heated air to treat for bed bugs, or any other insect or microorganism. Failing to control the aerosol generated during aggressive air mixing may be negligent.
Why Actively Heat Structures
Structures can be actively heated to kill bed bugs, termites, cockroaches and other insects, as well as to dry- out wet materials, accelerate off-gassing VOCs, and kill and/or reduce the concentration (load) of biological organisms within the structure. Active heating of structures constitutes a “green” approach to insect and organism eradication – it is not a chemical pesticide! In fact, structural heating has been prescribed for the treatment of residences for asthma patients.
Killing Insects and/reducing other biological organisms
Bed bugs specifically, and other biologicals, (e.g., fungi, bacteria, other insects, etc.), enjoy the creature comforts of our buildings and enjoy similar temperatures that us humans enjoy, (i.e., room temperature –
70F (21C)). Particularly, bed bugs gravitate to the warmth of the human body, carbon dioxide that humans exhale, tiny cracks and crevices, and darkness. Like most biological organisms, they suffer when heated to temperatures that are extreme. Most biological organisms do not survive temperatures above 135F (57C) and when structures are actively heated to temperatures of 145F (63C), or more, most biological organisms cease to survive – they die. Therefore, actively heating structures to elevated, lethal, temperatures is an effective method of bed bug control – it kills them.
Effectively Heating Structures
Effective structural heating requires a combination of elevated temperatures, temperature duration, and equal distribution uniformity of the elevated temperature coupled with controlled air movement using fans, pressure differences inside heated areas (relative to outside), and the capacity of the air-delivery and heater system. Effective structural heating is an active methodology; it is not passive.
Elevated Temperature and Duration
In order to increase temperatures within a structure, it is accomplished by delivering hot and relatively dry air into a treatment area. There are several methods of structural heating with hot, dry air. For example the heat source may provide electrically-generated heat using infrared heaters, or burning a fuel-gas via forced- air burners or boilers, and the heat can be delivered directly or indirectly, or both. The method of heat generation and the delivery method are somewhat irrelevant to this discussion regarding why actively heating structures without air filtration is dangerous. Consequently, the means and methods of heating structures will be limited in this narrative. However, suffice it to say that active structural heating involves elevated temperatures and requires holding the target temperature for a duration that is sufficient to achieve the intended goal, e.g., kill bed bugs.
Distribution uniformity
To achieve the goal of eradicating bed bugs or other insects, just as with drying, off-gassing chemical vapors, and/or reducing biological loads, the distribution of heat must be uniform and equal. If materials, buildings, rooms, furnishing, etc., are not heated uniformly and equally, and if lethal temperatures are not achieved,
the result is a “no kill”. If too high of temperatures are delivered into a treatment area, then damage to heat sensitive items may occur. Also, moisture and chemical vapors can be liberated from hot materials only to be reabsorbed into cool materials. Insects have legs and wings (i.e., they are motile) and they may move from hot, uncomfortable areas into areas that are less stressful. Moreover, materials that are only slightly heated, to a temperature of 90F to 100F (32C to 38C), may exhibit ideal conditions for some microorganisms (e.g., fungi, bacteria, protozoa, etc.) to flourish; as if they were in an incubator and their concentrations may actually increase due to (raised) temperatures that are less than lethal. Thus, effective structural heating must achieve a uniform and equal temperature increase to a target, lethal temperature.
Aggressive air mixing/currents
In order to achieve uniform and equal distribution of elevated temperatures within a structure or area being actively heated, aggressive air mixing must be employed. Hot air is more buoyant than cool air, and if not aggressively mixed, a heated room will have a hot ceiling and a cool floor, with varying degrees of temperature in between. When aggressive air mixing is employed, which is necessary for heating uniformly and equally, particulate aerosols will be generated – lots of aerosols! Experts have measured, via hand-held, direct-read laser particle counters, significant increases in particulate concentrations in contained structures when aggressive air mixing is employed, with or without heating. Increases in particulate concentrations have been measured 5 to 10 orders of magnitude above that of ambient and/or passive conditions, i.e., conditions prior to activating the fan units to create the aggressive air-mixing environment.
Aggressive air mixing is necessary to uniformly and equally distribute hot air when actively heating an area, to raise temperatures of target locations and materials. It should be anticipated that the aggressive air mixing will also create significant aerosols and distribute those aerosols far and wide; even into areas not targeted for the heat treatment effort. If not controlled, it is likely that surfaces (be it floors, furniture, counters, etc.) within the treatment area, post aggressive air mixing, are covered with a layer of fine particulate matter. This matter, having been released and distributed during the active heating process, may be extremely harmful to building occupants if not mitigated. In the case of bed bugs, pillows, blankets, sheets and the like are covered with particulate matter. Occupants’ head and nose are placed in direct contact with this particulate matter.
Controlled exhaust air
When structures are actively heated, the air within the treatment area may quickly saturate with vapors that need to be removed, and particulates that need to be filtered. Moreover, aggressive air mixing will distribute these out-gassed vapors similar to aerosol distribution. Vapor concentration can be controlled via controlled exhaust. Effective filtration will reduce particulates inside the treatment to safe levels and also within the exhaust air. Consequently, filtration will mitigate particulates released into the environment; where they may harm sensitive receptors downwind.
Aerosols Form When Structures Are Actively Heated
A known effect of active heating is the generation of significant concentration of aerosols. There are several mechanisms involved that contribute to the generation of aerosols and the mixing of particulates when structures are purposefully heated with hot air. As mentioned above, aggressive air mixing is substantive in the liberation and distribution of particulates. Aggressive air mixing also breaks-up matrixes and bundles of particles ( i.e., large aggregate particles are broken into many smaller particles.) Also significant is the drying aspects of hot air. Many hydrophilic organic particles have hydroscopic water molecules adsorbed onto them, thus increasing their weight. Heating increases the vapor pressure exhibited on these water molecules, liberating some of them, and this phenomenon makes the hydrophilic particle lighter in weight and more easily made airborne. Water molecules are also polar and small particles may be held together due to the attraction with polar water molecules. These small particles may be released when water
molecules are no longer present. Fungi, when pressured with aggressive air currents and/or drying air, are known to sporulate (release spores). Even small quantities of fungal biomass can be anticipated to release millions of mold spores when stressed by hot, dry air in an aggressive air mixing environment. Moreover, as the fungal biomass dries it can be anticipated to break apart and fracture in small particles, thus releasing many small mold products. Lastly, hot mixing air currents generate static electrical potentials along with the movement of particulates in the hot air. Static electrical potentials in the mixing air will affect particulates that are polar (i.e., have electrical potentials on their surface) and some will become airborne that may not necessarily do so. Bottom line…in a hot, aggressive, air mixing environment, significant concentrations of aerosols must be expected. Moreover, they must be mitigated. Otherwise a potentially harmful concentration of aerosols will be present in the air during treatment and residue (post-heat) on surfaces.
What Makes Airborne Particulates Dangerous
Large and small particulates – PM10’s, PM2.5’s, nano-particles
It is well known that it is the small particulates that cause the most damage to lung tissues when inhaled deep into the gas exchange region of the lungs, and very small particles can cross cell membranes. Large particles are typically trapped by impaction on mucous surfaces of the nose and throat, impingement on bronchi, and entrapment within cilia. Small inert particles, those much less than a micron, are thought to move in and out of the lungs with minimal affect, but this is not true of chemically reactive or sensitizing particles. Many atmospheric studies have confirmed that aerosols of an aerodynamic diameter of 10- microns or less, or PM10’s, are dangerous. More recent studies have looked at the damaging affects of smaller particulates, those that are near 2.5 microns in size, or PM2.5’s. There is current concern for engineered products referred to as nano-particles that are far smaller than 1 micron; yet their health affects are not fully understood at this time.
Of some relevance in this study of lung-damaging particulates is the difference between particles that are organic versus inorganic. Organic particles, in general, have a much lower density and less mass than most inorganic particles, and larger organic particles are more buoyant than most inorganic particles of similar size. In structures that are aggressively treated with hot air, both organic and inorganic particulates must be anticipated. In situations where biological particulates are of concern (e.g., water-damaged buildings with mold spores, mold fragments, dust mites, bacteria, etc.) the hazard of bio-aerosols cannot be underestimated because of their potential to be bio-reactive, toxigenic, and/or infectious. Moreover, inert airborne particles have been shown to contain microorganisms…essentially hitching a ride on the inert particle. Moreover, particulates cannot be thought of as unique, pure, or isolated. More often, airborne particles are clusters, bundles, and matrixes of a combination of several sub-particles, organic and inorganic, active and inert. A sampling of airborne particles generated during aggressive air mixing will detect major and minor fractions of fibrous and non-fibrous elements; inerts such as quartz, feldspars, and silicates; chemical sensitizers such as zinc and related corrosion products; organic sensitizers such as mold spores, pollen, and insect feces; and a host of other stuff.
Recent studies show inhaled particulates are dangerous
Studies have shown that the inhalation of small particulates, especially those less than 10- microns in size, may increase respiratory disease, cause lung damage, and induce asthma, allergic reactions, cancer, and premature death. Most affected by the inhalation of small particulates are children with young and developing lung tissue, people with respiratory dysfunction and/or sensitivity, and people with compromised immune systems. It is speculated that some bio-aerosols may trigger hypersensitivity in compromised individuals. Moreover, there are claims by some indicating that an acute exposure to bio- aerosols may also trigger hypersensitivity. This said, and given that hot, dry, aggressive air mixing environments have all the attributes to generate and distribute significant concentrations of aerosols,
aerosol control is essential. Given that structural heating often occurs in buildings that are water-damaged, exhibit uncontrolled growth of fungi and bacteria, or excessive and uncontrolled growth of insects (e.g., bed bugs, fleas, termites, etc.), the control of harmful bio-aerosols generated when actively heating a structure for bed bugs or other insects or for biological remediation is a necessity. Not controlling aerosols generated within an aggressive air mixing treatment area is negligent; especially when given the fact that there are effective controls that can mitigate aerosols.
Engineering Controls – Air Filtering to Remove Aerosols
Exhaust alone is not effective or prudent to mitigate aerosols generated in an aggressive air mixing
environment. Solely exhausting air from an area subject to aggressive air mixing will assist in diluting the concentration of aerosols within the treatment area, however, a significant portion of the aerosol will remain and settle-out, and the rest is emitted with the exhaust air. If not controlled, even the particulate- laden exhaust air may be dangerous to receptors downwind from the point of exhaust. The most effective and practical method of capturing and removing the aerosol is through the prodigious use of fan units equipped with high efficiency particulate air (HEPA) filter media. HEPA-filtered fan units have a proven ability to mitigate particulate aerosols and where enhanced filtration is warranted, ultra-HEPA filter media is available. Moreover, when HEPA-filtered fan units are incorporated into remediation projects where biological control is warranted and where biologicals may become airborne (e.g., mold spores), capturing the bio-mass on a filter media is similar to other methods of physical, gross removal, i.e., the filter is a physical removal method. HEPA air filtration is effective and warranted to control particulate aerosols, but several elements must be designed into the use of HEPA-filtered fan units to achieve efficacy.
Sized for rate of air exchange
To control aerosols, HEPA-filtered fan units must be adequately sized, in number and in capacity (i.e., flow rate), to cycle sufficient air through the treatment area being subjected to aggressive air mixing. In some circumstances, a rate of 4 to 6 air exchanges per hour (AE/hr) may be adequate to control the aerosol generated. In other circumstances 10 to 20-AE/hr, or more, may be necessary to achieve control in soiled (dirty) locations. If the area to be heat-treated is very clean, 1-AE/hr may be adequate to maintain ambient conditions (i.e., pre-mixing particulate concentrations). Only through the use of direct read aerosol monitors can the immediate concentration of airborne particulates be measured in areas subjected to aggressive air mixing and, subsequently, the capacity of filtration and air exchange rates thus determined; to mitigate aerosol concentrations to ambient conditions or less.
The environmental remediation industry’s standard of care is based on 4-AE/hr, then modified (based on direct-read measurements) as conditions warrant. In lieu of using direct-read aerosol monitors, areas being heat-treated, when coupled with aggressive air mixing, should use HEPA filtered fan units sized for a minimum air exchange rate of 4 per hour.
Controlled input and output
In situations where it is necessary to exhaust air laden with moisture and/or chemical vapors, some HEPA- filtered fan units’ exhaust can be ducted-out of the treatment area to remove the vapors. In doing so, the exhaust air is clean and filtered of particulates. Other HEPA-filtered fan units can sit inside the treatment area, un-ducted, and cycle air through the filter element – solely to capture particulates and physically remove them. Where exhaust is warranted, it must be controlled and the flow rate of moisture-chemical laden air removed from the treatment area must be measured relative to the flow rate of air (hot or ambient) into the treatment area. Too much or too quickly removed, and the treatment area will not rise in temperature if heating is a goal; this is especially critical when the treatment area is indirectly heated via heat exchangers. Too high an input flow of hot air into a treatment area and the movement of aerosols may be difficult to control; thus air filtration is essential to mitigate the movement of particulates into spaces
that are not part of the treatment area when high input flow rates are used. When HEPA-filtered fan units are judiciously used, the movement of “clean” hot air within the treatment area and into other “non- treatment” spaces does not carry the risk of particulate contamination.
Located to mitigate dead-zones
HEPA-filtered fan units must be located in sufficient quantity and capacity to achieve an air exchange rate, and so located to filter air in locations that would otherwise allow particulates to settle-out. Corners, small alcoves, nooks, and enclosed spaces are typical locations where air mixing currents may be limited or reduced, and these are locations where an un-ducted HEPA-filtered fan unit can assist and enhance air mixing currents, as well as capturing particulates (for physical removal) that might otherwise settle-out (in these areas).
Cleaning the Air – Before, During and After Heating
In most circumstances, areas that will be treated with hot air also warrant cleaning, i.e., they are dirty, soiled, and/or contaminated. During the time that equipment is being mobilized and set-up to generate and deliver hot air into a treatment area, HEPA-filtered fan units should be one of the first pieces of equipment placed, put into operation, and activated. They can immediately begin to capture aerosols generated by activities taking place to prep and deliver heat to a treatment area. When hot air is being delivered into a treatment area and being actively distributed therein, HEPA-filtered fan units should be operating continuously and without interruption. Once the target temperature and duration is reached and the cool- down phase begins, HEPA-filtered fan units should still be continuously operating. Moreover, they should continue to operate during the demobilization effort and be one of the last pieces of equipment turned-off and packed out; thus mitigating particulate aerosols the entire event, from beginning to end.
Measuring effectiveness
Where heat treatment is performed, an easy and effective method of measuring the effectiveness (post- treatment) of particulate removal is with a tape lift – similar to the tape lift method used to determine to presence-species of mold on a surface. Particles adhered to the tape lift can be evaluated and identified using a polarized light microscope. In some circumstances it may be useful to compare surfaces within the treatment area to surfaces outside of the treatment area. This said, the tape lift and particle identification should not replace the application and use of direct-read, real-time particle counters – hand-held devices that can provide real-time data on the effectiveness of dust mitigation measures during aggressive air mixing efforts.
Summary
In summary, heating structures or areas within structures is fast becoming the most effective bed bug eradication method and as a remediation technique. Effective structural heating relies on equal and uniform distribution of the hot air and this is best accomplished with aggressive air mixing. However, aggressive air mixing generates significant aerosols. Methods exist to control the aerosols and they should be judiciously implemented to do so – HEPA-filtered fan units are the best available control technology to mitigate aerosols generated during active heat treatment. Failing to control the aerosol generated during an effort that employs aggressive air mixing may be negligent, because studies have indicated that it is very likely to be harmful or injurious to persons exposed to the post-treatment aerosol.
About Michael Geyer, PE, CIH, CSP
An expert in mitigating chemical-biological contaminants in buildings, conducting property conditions assessments, improving indoor air quality, mitigating vapor intrusion, characterizing landfill gas, and building off-grid homes.
Michael has 20-years of professional experience in environmental engineering, preceded by 15-years of construction experience working in the trades, building off-grid power systems, and supervising building projects. He has built hundreds of residential homes (both tract developments, custom houses and remote ranch-style homes) and commercial buildings, and many special-use structures, e.g., theater, sport venue and schools. His unique construction experience has been valued by developers/owners building on compromised property (e.g., Brownfields) with known chemical or biological hazards. He specializes in high- hazard construction efforts and those impacted with methane, hydrogen sulfide, VOCs or radon. His experience in the remediation of buildings compromised with biological agents using heat as a remediation technique, is extensive.
Michael’s current work includes: mitigating soil-gas vapor intrusion (VI); assessing outdoor and indoor air quality (IAQ); conducting building envelope and property condition assessments (PCAs); designing engineering controls to enhance occupant safety; and oversight of construction projects impacted by chemical hazards. Michael also designs and builds off-grid and utility inter-tie power systems, super- insulated cabins and high-performance homes for private parties. Michael contracts with all types of clients, including: municipalities, developers, private property owners/managers, and industrial sector clientele, as well as professional practice firms such as engineering, architecture, insurance and law. Michael is often retained by counsel to assist litigation, review case documents, provide expert opinion, and support arbitration. Michael also shares his considerable knowledge with others. He routinely presents case studies at national conferences and seminars and is often requested to provide classes at industry-sponsored professional development courses (PDCs), and for five years he has volunteered his time to the Kern County (California) Solid Waste Management Advisory Committee. He is active with his community, his 4-H club and supports home-education.
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2. U.S. Department of Labor, Occupational Safety & Health Administration, OSHA Technical Manual – Section III: Chapter 2, Indoor Air Quality Investigation. http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_2.html
3. California Environmental Protection Agency, Air Resources Board, ARB Fact Sheet: Air Pollution Sources, Effects and Contro http://www.arb.ca.gov/research/health/fs/fs2/fs2.htm
4. American Lung Association: Selected Key Studies on Particulate Matter and Health:1997 – 2001. http://www.kintera.org/atf/cf/%7B7A8D42C2-FCCA-4604-8ADE-
7F5D5E762256%7D/PMSTUDIES.PDF
- 5. Baron, Paul A, PhD. National Institute of Safety and Health/DART – Measurement of
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