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Indoor Environmental Quality!

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Indoor Environmental Quality
In the modern world, people spend more than 90% of their time indoors. The spaces we design to accommodate work, learning, play, and life can play a significant role in improving people’s health, wellness, and happiness. Indoor environmental quality (IEQ) indoors is driven by all the systems that make up a building, including envelope, HVAC, lighting, and acoustics. All the variables that go into these systems are interrelated and can be considered synonymous to the systems of a body. They operate in cooperation and influence each other. Therefore, IEQ is the combined interrelation between Indoor Air Quality (IAQ), Thermal Comfort, Lighting, and Acoustics. This post takes a dive into the topics of IndoorAir Quality and Thermal Comfort.
Thermal Comfort
Thermal comfort is defined as “the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation." Thermal comfort in the body is provided through a homeostatic system that balances heat gains and losses to maintain the body’s core temperature within its optimal range, 97-100°F (36-38 °C), and is regulated by the hypothalamus.

The indoor thermal environment not only impacts our buildings’ energy use, as cooling and heating accounts for approximately half of a building’s energy consumption, but also plays a large role in the way we experience the indoor environment. Thermal comfort is linked to health, well-being and productivity and is ranked as one of the highest contributing factors influencing overall human satisfaction in buildings. Due to its influence on the integumentary, endocrine and respiratory body systems, thermal comfort can impact multiple health outcomes. For example, exposure to cold air and sudden temperature change can trigger asthma in adults. Leading research also indicates employees perform 6% poorer when the office is overheated and 4% poorer when the office is cold.

A comfortable thermal environment that satisfies all occupants is challenging to achieve due to individual preferences and possible spatial and temporal variations in the thermal environment. Therefore, there is a need for a holistic approach to thermal comfort that can satisfy the individual preferences of all (or nearly all) building users. Correctly sized HVAC equipment is essential for optimal thermal comfort. Building HVAC systems should be designed to monitor and control for variations in indoor temperature, radiant heat transfer through the building envelope, relative humidity and air movement.
ASHRAE Standard 55 - Thermal Environmental Conditions for Human Occupancy – uses six factors in determining acceptable thermal environment for the representative occupants in a space at steady state. Four are environmental factors, meaning they are under control of the design team. While two are personal factors, totally unique to each individual:
  1. Metabolic rate (personal factor)
  2. Clothing insulation (personal factor)
  3. Air temperature (environmental factor)
  4. Radiant temperature (environmental factor)
  5. Air speed (environmental factor)
  6. Humidity (environmental factor)
Predicted comfort condition tools using ASHRAE 55 are available for use, the most popular being the CBE Thermal Comfort Tool.

Metabolic Rate
The level of activity of the occupant is associated with their metabolic rate, which in turn affects the thermal conditions at which they are likely to be comfortable. Of course, the standard does not regulate or in any way try to control occupant activities. Rather, the expected or observed activity is used as an input to thermal comfort determination.
Clothing Insulation
Clothing insulation values are predicted based on what a representative occupant is likely to wear while being within the space. ASHRAE Std. 55 allows several methods for determining the clothing insulation value for the representative occupant, which can also vary by season and space type within the building (e.g. occupants in a commercial kitchen would be dressed differently than students in a classroom). Insulative properties for chairs in which occupants are primarily seated – like an office setting – can also be considered.

Air Temperature
Temperature and thermostats are the most common thermal comfort and indoor air criteria building occupants are familiar with. Looking at ASHRAE Std. 55 with more specificity, recommended temperature ranges perceived as “comfortable” are 73 to 79°F in the summer and 68 to 74.5°F in the winter.
International Energy Conservation Code (IECC) Section 302.1 dictates interior design temperatures used for heating and cooling load calculations shall be a maximum of 72°F for heating and a minimum of 75°F for cooling. These design values drive proper sizing ofmechanical equipment and the HVAC system. While the code does not address over-sizing equipment, it is not enforceable without establishing these exact design parameters.
The energy code also dictatessetback (403.4.2.1) and deadband (403.4.1.2) requirements.The Setback controls shall be configured to temporarily operate the system to maintain zone temperatures down to 55°F or up to 85°F during unoccupied hours, while the Deadband requires thermostatic controls be configured to provide a temperature range of ≥ 5°F within which the supply of heating and cooling energy to the zone is shut off or reduced to a minimum.
Interior design temperatures are also required by Section 1203 of the International Building Code (IBC) and Section 602.2 of the International Property Maintenance Code (IPMC), which includes similar requirements for housing and property maintenance.
The IBC states that “interior spaces intended for human occupancy shall be provided with active or passive space heating systems capable of maintaining an indoor temperature of not less than68°F (20°C) at a point 3 feet (914 mm) above the floor on the design heating day.” Exceptions are in place for spaces where the primary purpose of the space is not associated with human comfort, and for Group F (factory), H (high-hazard), S (storage), or U (utility) occupancies.

Radiant Temperature
Mean radiant temperature is one of the six core thermal comfort parameters. It is influenced by a surface material’s ability to absorb or emit radiant heat, the extent to which the surface area is exposed to the person (view factor) and the temperatures of the surrounding objects. Non-uniform thermal radiation can result from cold windows, uninsulated walls, equipment and improperly sized heating panels, all of which can cause local discomfort.
Thermal radiation effects due to surface temperatures are used in determination of mean radiant temperature and operative temperature and local discomfort caused, for example, by a cold window on one side and a hot wall on the other, an effect referred to as “radiant asymmetry.”

Air Speed
Basic engineering states that the three modes of heat transfer are conduction, convection, and radiation.
Air speed is important to the rate of convective cooling of the body as well as its rate of evaporative heat transfer. This effect can be room-wide or local. It may be experienced as a beneficial cooling effect (using fans to create convective “cooling” in the summer in lieu of lowering thermostatic setpoints) or as a negative effect, as in draft. Draft is considered by the standard to be a local effect (i.e., local to a person and not to the entire space). The velocity of air delivered to a space should be considered in both heating and cooling application design and can be measured with an anemometer in the space.

Humidity can influence degradation of building materials and the ability of the human body to release heat through evaporation. If the humidity is too high, the human body has a limited capacity to cool down through sweating. Elevated humidity can lead to increased off-gassing; for example, an increase in relative humidity of 35% can increase the emissions of formaldehyde by a factor of 1.8 to 2.6. Moreover, high humidity may promote the accumulation and growth of microbial pathogens including bacteria, dust mites and mold, which can lead to odors and cause respiratory irritation and allergies in sensitive individuals. Conversely, low humidity can lead to dryness and irritation of the airways, skin, eyes, throat and mucous membranes. Low relative humidity is also associated with longer survival (slower inactivation) of viruses.

There are two ways to define the humidity, or water content, of air – absolute (measured in grains of moisture per pound of air, grains / lb) and relative (measured in percent, %). People are generally only familiar with the concept of relative humidity, even though it doesn’t tell an accurate story of the true moisture quantity in the air. Relative Humidity To have meaning, a relative humidity reading must be associated with a dry bulb air temperature. The hotter the air, the more moisture it can hold.
Relative humidity (RH) is the actual amount of water vapor in the air as a percentage of the maximum amount of water vapor which the air could hold at a given temperature.
If the amount of water vapor in the air were held constant as the temperature was increased, this would cause the relative humidity to fall, because the warm air would now be able to hold more water vapor then when it was cool.
In the winter, as cold moist outdoor air is brought indoors and heated, it becomes warm, dry air just by being heated. Air at 20°F & 70% RH, when heated to 72°F, will have a relative humidity of just 8%. This phenomenon is demonstrated in the table above. Absolute Humidity Absolute humidity is constant regardless of air temperature and measured in grains. A grain is a unit of measurement of mass, nominally based on the mass of a single virtual ideal seed. For reference, 3,500 grain = ½ pound (lb) of moisture in the air. It is an absolute measurement, which means it does not depend on the dry bulb air temperature.
Consider the example below.

The small glass on the right represents air at 30°F. It holds 1-1/2 ounces of water and is 80% full (80% RH).
The large glass on the left represents air at 70°F. It holds the same 1-1/2 ounces of water, but in this larger glass it only fills 15% of the space (15% RH).
Absolute humidity (ounces) stays the same, while relative humidity (%) changes with regard to the volume of the space (temperature of the air).

Indoor Air Quality (IAQ)
Concern about indoor air quality (IAQ) and the study of air quality issues is a fairly recent phenomenon. Some of the earliest documented studies occurred in Scandinavia in the mid-1960s and were focused primarily on thermal comfort issues. These early IAQ studies also primarily involved comparing indoor air to outdoor air. The levels of outdoor pollution were considered a primary concern and the goal was to ensure that indoor air was of better quality than polluted outdoor air.
As studies increased in sophistication, other measurable factors came into play. Building construction materials and techniques changed radically. A reduction in ventilation / outside air, in the interest of saving energy became a concern and, finally, people realized that pollutants could originate from within a building and result in Sick Building Syndrome, Building-Related Illness, Chemical Sensitivity, and/or Environmental Illnesses (with new medical terminology gaining more attention every day as a result).
When considering IAQ, we are looking to compare not to what is considered “normal” and not to established hazardous material limits, but to progressive limits and evolving standards since different people react differently to different levels of different substances. There is no universal reaction to a measured amount of a particular material (similarly to how people respond differently to different thermal comfort conditions). Determining ‘acceptable’ and ‘unacceptable’ levels of indoor pollutants can be challenging, so it is necessary to look to multiple references and sources.
Typical symptoms caused by poor IAQ vary greatly according to an individual’s sensitivity and may include chills, sweating, eye irritation, allergies, coughing, sneezing, nausea, fatigue, skin irritation, breathing difficulties, and others. Unfortunately, there are currently no federal regulations governing exposure limits in non-industrial indoor environments, though IAQ has gained attention in light of the current coronavirus pandemic.
The World Health Organization (WHO) estimates that more than 30 percent of all commercial buildings have significant IAQ problems. And data from the U.S. Department of Labor attributes the primary source of poor IAQ to inadequate ventilation at 52%, followed up closely by contamination from inside the building at 16%). For this reason, it is critical that we take a proactive approach to Indoor Air Quality.

Ambient (Outdoor) Air Quality
The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (40 CFR part 50) for pollutants considered harmful to public health and the environment. The Clean Air Act identifies two types of national ambient air quality standards. Primary standards provide public health protection, including protecting the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.
The EPA has set National Ambient Air Quality Standards (NAAQS) for six principal pollutants, which are called "criteria" air pollutants. Periodically, the standards are reviewed and may be revised. The current standards are listed for Carbon Monoxide (CO), Lead (Pb), Nitrogen Dioxide (NO2), Ozone (O3), Particle Matter (PM), and Sulfur Dioxide (SO2).
ASHRAE Standard 62.1 Section 4 specifically addressed Outdoor Air Quality and requires an investigation to be completed prior to finalization of the HVAC ventilation system design. In the U.S. compliance status shall be either in “attainment” or “nonattainment” with NAAQS, as described above. Areas with no U.S. Environmental Protection Agency (USEPA) compliance status designation shall be considered “attainment” areas. The USEPA list of nonattainment areas can be found at Air quality data collected at outdoor monitors across the U.S. can be found Local Air Quality Standard 62.1 also requires an observational survey of the building site and its immediate surroundings
conducted during hours the building is expected to be normally occupied to identify local contaminants from surrounding facilities that will be of concern if allowed to enter the building. This survey should report out the following at a minimum:
  1. Regional air quality compliance status
  2. Local survey information: a. Date of observations, b. Time of observations, c. Site description, d. Description of facilities on site and on adjoining properties, e. Observation of odors or irritants, f. Observation of visible plumes or visible air contaminants, g. Description of sources of vehicle exhaust on site and on adjoining properties, h. Identification of potential contaminant sources on the site and from adjoining properties, including any that operate only seasonally.
  3. Conclusion regarding the acceptability of outdoor air quality and the information supporting the conclusion
Carbon Dioxide (CO2)
While carbon dioxide (CO2) in and of itself is not a contaminant, it is directly attributable to human occupancy levels in a building, and a useful proxy to determine if appropriate levels of outdoor / ventilation air are entering the breathing zone for occupants. Also, elevated CO2 levels can cause cognitive and health issues at high concentrations indoors.

OSHA Technical Manual (section iii, chapter 2), 1999, states that 1,000 ppm CO2 should be used as an upper limit for indoor levels, as a guideline for occupant comfort.>1000 ppm indicates inadequate ventilation; complaints such as headaches, fatigue, and eye and throat irritation will be more widespread.

ASHRAE Standard 62.1-2013 suggests maintaining a steady-state CO2 concentration in a space no greater than about 700 ppm above outdoor air levels will result in a substantial majority of occupants being satisfied in respect to human bioeffluents (body odor). Additional ventilation may be needed to dilute building generated pollutants. This standard also defines adequate ventilation for specific use designed spaces. For example, 17 cfm (8.5 l/s) per person of dilution air is suggested for office spaces (because such spaces have additional pollutants introduced from copiers, laser printers, etc.), which translates to a CO2 concentration of roughly 600 ppm above outdoor air levels.

American Society of Testing and Materials (ASTM International) studies have concluded that about 7.5 L/s of outdoor air ventilation per person will control human body odor such that roughly 80 % of unadapted persons (visitors) will find the odor at an acceptable level. These studies also showed that the same level of body odor acceptability was found to occur at a CO2 concentration that is about 650 ppm(v) above the outdoor concentration. D6245-12 Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation, 2012

US Environmental Protection Agency (USEPA)
Testing for Indoor Air Quality, Baseline IAQ, and Materials, 2009, section 5 states that "Acceptance of respective portions of buildings by the Owner is subject to compliance within specified limits of IAQ contaminant levels. CO2 not to exceed 800ppm."
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With the advent of Covid, indoor sports activities have been interrupted and banned due to the danger of contagion among sportspeople and the public. In this pandemic context, some public administrations are trying to fight the virus in the best way.
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The Hi-Tech filtering solution for ventilation systems.

With increasing air pollution, the demand for better air filtration is increasing, just as we try to contain the energy impact of the plants as much as possible with a view to sustainable development: these needs appear in stark contrast to each other, however active electrostatic filters are capable of providing an effective solution.
In fact, any "mechanical" type air filter, ie whose efficiency depends mainly on phenomena of mechanical interference between the particles in transit and the filtering fibrous matrix, undergoes a progressive increase in pressure drops, due to the accumulation of transverse deposits with respect to the air flow.
For example, a medium-high efficiency paper filter, class F7-F8 according to UNI EN 779, can be characterized by initial pressure drops of 100-150 Pa, which can increase up to 450 Pa at the end of its operating life. Over the operating time, the increase in pressure drops leads to an increase in the electricity absorbed by the fans to guarantee the design flow rate, or a progressive reduction in the flow rate in systems that are unable to correctly compensate.
Active electrostatic filters, on the other hand, "remove" the suspended particles from the air flow and precipitate them on plate collectors, which are arranged along the direction of crossing. Thanks to this property, electrostatic filters offer very low pressure drops, almost constant during normal operating life, which ends when the thickness of the deposit begins to disturb the electric field, instead of preventing the passage of air, as happens in "mechanical" filters. In the case of an Expansion Electronic FE active electrostatic filter, for example, for the same efficiency class considered for the comparison with the "mechanical" filter, the pressure drops are constant and are around 30 Pa.

Many studies have shown that one of the biggest problems in ventilation systems is the reduction in flow that occurs after about 2-3 years of operation.
This fact is normally caused by the accumulation of dust and dirt on fans, batteries, channels and other system components. Furthermore, this contamination is the ideal medium for the proliferation of bacteria, microorganisms and molds which, in turn, determine an unhealthy ventilation system. Furthermore, a reduction in flow means that the ventilation system does not fulfill one of its primary functions.
If it is true that the filtration system is the main defendant, the solutions can alternatively be:

a) Increase the frequency of cleaning operations on the air handling unit, batteries, fans and ducts.
b) Improve the filtration system by adopting filters that have a good efficiency on the whole spectrum of dust (coarse, thin and ultra-thin).

Expansion Electronic's FE electrostatic active filters fully meet this second requirement.

Achieving environmental and economic improvement goals is also increasingly a concern in the HVAC sector.
Considering the type of "mechanical" filters, it can be seen that the higher the class of filtration, the more frequent the intervention for replacing the filter must be and proportionately the capacity of pollutant accumulation will be lower.
Expansion Electronic's FE electrostatic active filters have a threefold advantage over "mechanical" filters:

a) The storage capacity of pollutant is considerably higher. For example, for an FE 600 filter (592x592), the storage capacity is 600 g of DEHS ISO 12103-A2 dust, about four times higher than that of an H10 filter. This reduces the frequency of maintenance interventions and the consequent costs for the disposal of "mechanical" filters.
b) Unlike the "mechanical" filters, the active electrostatic filters can be regenerated and reintegrated into the system. Their cleaning takes place through water and detergent. If the maintenance is carried out correctly, the active electrostatic filters can last many years (on average 10-15).
c) As previously explained in the section dedicated to energy efficiency, active electrostatic filters have significantly lower pressure drops, allowing for significant energy savings.

In ventilation systems that install "mechanical" filters, there is a possible formation and release of toxic microbial products from decomposition, such as endotoxins.
On the contrary, the electrostatic filter has a high antibacterial power due to its high efficiency on submicronic particles and the action of the electric field. The results of some tests carried out at the ILH Institute of Air Hygiene in Berlin and the Policlinico San Matteo in Pavia show that the filter systems of Expansion Electronic are able to eliminate air-dispersed bacteria, yeasts and molds from the air with an efficiency ranging from 98.53% to 99.96%.

In indoor environments, the presence of ultra-fine powders (PM 1, PM 0.4 and lower) is increasingly found, which reach values ​​much higher than those found outdoors. This fact is mainly due to the accumulation of dust resulting from the introduction of outside air (especially winter) not properly treated, and to the difficulties related to their elimination.
99.9% of all the particles present in the atmospheric air are less than 1μm.
Ultra-fine powders and nanopowders are the most dangerous for health as they reach the lung alveoli and from here enter the bloodstream. They are the most difficult to catch.
A marked filtering action towards the ultrathin air dusts allows to act decisively on the prevention of many pathologies, even serious ones attributable to the effect of the mineral nano-micro-powders such as chromium, iron, lead, etc. (see the new medical discipline of nanopathology).
The choice of particularly effective filters towards ultra-fine dust is a guarantee for decontamination from microorganisms (bacteria-viruses) present in the air and their decomposition which is one of the causes of sick building syndrome.
The electrostatic active filters of the Expansion Electronic FE series have a high filtration efficiency on all aspects of dust. As an example, at a filter crossing speed of 1.5 m / s, an FE filter offers a filtration efficiency of 98.8% on a particle size of 0.4 µm and 98.4% on 0.13 µm.
To achieve these performances with "mechanical" filters it is necessary to use absolute filters.

The UNI 11254 standard classifies active electrostatic filters into four filtering grades (A, B, C, D). The efficiency taken into consideration in this standard is the average Em efficiency on the grain size of DEHS of 0.4 μm.
A homogeneous comparison with the "mechanical" type filters is not possible, since the efficiency classes of the latter take into consideration:

a) The average filtration efficiencies over the useful life of the filter which is not constant, but grows with the impregnation of dust by the particulate filter with a particle size of 0.4 μm (class F, EN 779).
b) The minimum filtration efficiencies for particulates with a particle size of 0.3 μm (class H, EN 1822).

However, FE filters can be combined with mechanical filters (classes F or H) based on their performance towards the particle size.
The same FE filter offers, in terms of performance, an increasing filtration efficiency with decreasing air passage speed.
At a speed of 4 m / s a ​​FE filter will be comparable to a "mechanical" class F7 filter, while at 1.5 m / s its filtration efficiency will make it comparable to a class H12 filter. Therefore, in a system with a variable flow rate, with an active electrostatic filter, the minimum efficiency class will be that obtained at the maximum flow rate and will grow for lower flow rates. This peculiarity does not exist for mechanical filters that maintain the same efficiency class at the different operating flow rates, although the degree of efficiency is minimum with a new filter.

Choosing an inadequate filter for the air treatment unit will make the performance of the system poor because most of the ultra-fine dust contained in the air passes through the system and enters the circulation. In the long run, this causes the batteries, the fan, the channels to become dirty and a high concentration of ultra-fine powders that are difficult to eliminate in the treated environments.
The choice of a high efficiency filter considerably reduces the effects mentioned above. The high performance of Expansion Electronic's active electrostatic filters towards fine (PM 2.5), ultra-thin (PM 1) and nano (PM 0.4) dusts make it the ideal choice for all those who want to obtain from a ventilation system. a high degree of air hygiene, markedly reduced maintenance costs, significantly reduced energy costs, large storage capacities (600g) and, last but not least, constant air flow and efficiency over time.
Having a high efficiency on the whole spectrum of dust means inducing high air quality especially from a hygiene point of view (bacteria, spores, molds, viruses, etc.), as well as safeguarding the system (batteries of exchange, channels, etc.) with important returns on maintenance costs.

The active electrostatic filter is a high precision filter, composed of noble materials and is not intended for "disposable".
The higher initial cost will be amortized over time (2.5 - 3.5 years) for:

a) lower maintenance costs;
b) lower energy consumption compared to a high quality Indoor air quality.

It can therefore be understood that active electrostatic filters allow a return on investment which must be considered in all respects an important parameter of choice.
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In ensuring the safest, most sanitized space for your guests—the most protected from the New Coronavirus (2019-nCoV)—ions are your best friend. So says Steve Levine and Tony Abate from AtmosAir Solutions. Their company’s technology has been proven to eliminate the Coronavirus, other viruses, bacteria, fungi and allergens. Levine is President & CEO of the Fairfield, Conn.-based company and Abate is Chief Technology Officer.
At the core of AtmosAir systems is Bi Polar Ionization technology. Within an HVAC system or as a standalone unit, ionization tubes are placed. As airflow passes through the tubes, Bi Polar—positive and negative—ions are created that persist for up to 300 seconds. In the case of a virus such as the Coronavirus, the ions destroy the virus surface structure on a molecular level. As a result, the virus cannot infect, even if it enters the body. The ions also bond to dust and mold particles, break down germs and odors at their source, and break down toxic gasses.
There are three primary ways for the Coronavirus to spread—through person to person contact, by touching a surface that has the virus, and by breathing in microscopic droplets expelled by someone with the virus.
“The ions that we produce pack the occupied space,” Abate says. “They saturate the space and go anywhere the conditioned air will go. “Our system can continuously disinfect the air and surfaces. The system offers another layer of protection against the droplets.”

‘Active’ Form of Air Purification
Unlike a passive system that draws air in and then “filters” it, AtmosAir technology creates the ions once the air flows through the system. “It is an active form of air purification,” Abate says.
Ionization is nature’s air cleaning process. Whereas, unique environmental conditions contribute to ion concentration in excess of 5,000 ions/cm3 near waterfalls and high mountains, ion levels can be as low as 75 ions/cm3 in some indoor locations. Bi Polar Ionization restores ion levels.
Because AtmosAir removes contaminants from the air, less makeup air is needed in a space—up to 50 percent less. According to Levine, HVAC system size can be reduced by 15 percent and energy consumption can be reduced by 30 percent. “If designed into a project at the outset, your HVAC system does not need to be quite as big,” Levine says. The life of HVAC equipment and filters can also be extended.
When asked what advances have been made to his company’s systems since the company was founded in 2007, Levine said, “Now we have incorporated sensors into the technology so you can measure the air quality on a real-time basis. We have also advanced the tubes so that they last 2 years—18,000 hours.” AtmosAware sensors measure different environmental conditions such as TVOC (total volatile organic compound), ozone, and relative humidity. The AtmosSmart logic-based controller interprets the data and automatically adjusts ion intensity to ensure optimal levels and air cleaning performance are maintained, 24/7.
An AtmosAir system is scalable, Levine adds—from a PTAC to a central air system. “We just did 140 hotel rooms in Tulsa. They are integrated into every hotel room in the fan coil unit.”
In addition to the direct physical public health, cost and energy savings benefits, bipolar ionization can be part of a wellness program. Levine says all of Hilton’s Five Feet to Fitness rooms will have AtmosAir purification. Some hotels are marketing rooms with AtmosAir systems as allergy and asthma proofed. In general, enhanced air quality has been proven to result in improved worker productivity, less sickness, and less missed work time.
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The spread of the Covid-19 is not only limited practicing social distancing but also combating the indoor air pollution.

Many people might be tempted to think that staying indoors means to be safe from air pollution, but research shows that this is far from the case. Air pollution can occur indoors, too, and has been linked to occurrences of headaches, dizziness, lack of concentration, and fatigue. The World Health Organization calls this “sick building syndrome.”

In the developed world, we already collectively spend around 90% of our time indoors. With these numbers increasing as a result of the coronavirus pandemic, managing indoor air pollution is even more important.
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The World Health Organization (WHO) must take swift action to establish global guidance on indoor air quality to reduce the spread of airborne bacteria and viruses in buildings, urges a new petition

A new petition has called on the WHO to take decisive action to establish global guidance on indoor air quality, with a clear recommendation on the minimum lower limit of air humidity in public buildings.

Supported by members of the global scientific and medical community, the petition is designed to not only increase global awareness on the role indoor environmental quality plays in physical health but also to call on the WHO to drive meaningful policy change.

As Covid-19 continues to put pressure on health systems and the economy globally, the group calls on the WHO to review the extensive research that shows an indoor humidity level of between the 40%-60% relative humidity (RH), is the optimum threshold for inhibiting the spread of respiratory viruses such as influenza.

Keep indoor air at 40-60%

Professor Dr Akiko Iwasaki PhD, The Waldemar Von Zedtwitz Professor of immunobiology and professor of molecular, cellular and developmental biology at Yale, and an investigator for the Howard Hughes Medical Institute said: “90% of our lives in the developed world are spent indoors in close proximity to each other.
“When cold outdoor air with little moisture is heated indoors, the air’s relative humidity drops to about 20%. This dry air provides a clear pathway for airborne viruses, such as Covid-19.
“That’s why I recommend humidifiers during the winter, and why I feel the world would be a healthier place if all our public buildings kept their indoor air at 40 to 60% RH.”
Evidence shows the important role indoor humidity levels play in preventing virus transmission and improving immune system response.

There are three key notable findings:
  • Breathing dry air impairs our respiratory immune system’s ability to efficiently capture, remove and fight airborne viruses and germs, rendering us more vulnerable to respiratory infections.
  • When the RH is lower than 40%, airborne droplets containing viruses, such as SARS-CoV-2, shrink through evaporation making them lighter. This enables the particles to float for longer in the air, increasing the likelihood of infection.
  • The vast majority of respiratory viruses suspended in dry atmospheres survive and remain infectious for much longer than those floating in air with an optimum humidity of 40-60%RH.
Optimum humidity can improve indoor air quality
One of the leading forces in the charge for a globally recognised 40-60%RH guideline for public buildings, Dr Stephanie Taylor MD, infection control consultant at Harvard Medical School, ASHRAE distinguished lecturer & member of the ASHRAE Epidemic Task Group, said: “In light of the Covid-19 crisis, it is now more important than ever to listen to the evidence that shows optimum humidity can improve our indoor air quality and respiratory health.
“It is time for regulators to place management of the built environment at the very center of disease control. Introducing WHO guidelines on minimum lower limits of relative humidity for public buildings has the potential to set a new standard for indoor air and improve the lives and health of millions of people.”
Dr Walter Hugentobler, MD, general physician, former lecturer Inst. of primary care at the University of Zürich, added: “Raising air humidity by humidification reduces the risk of virus spread in hospitals and other buildings at low-cost and without causing negative effects.
“It can also be easily implemented in public buildings, both in private and workplace environments with relative ease. Humidification gives people a simple means of actively combatting seasonal respiratory infections.”
According to the group, if the WHO publishes much-needed guidance on minimum lower limits of humidity, building standards regulators around the world would be encouraged to act urgently.

If these recommendations were implemented, the following effects could benefit global health systems and the world economy:
  • Respiratory infections from seasonal respiratory viruses, such as flu, being significantly reduced
  • Thousands of lives saved every year from the reduction in seasonal illness
  • Global healthcare services being less burdened every winter
  • The world’s economies massively benefiting from less absenteeism through illness
  • A healthier indoor environment and improved health for millions of people.
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