Chinavirus infection control in existing building design

COVID-19 infection control in existing building design

The recent spread of the pandemic chinavirus or coronavirus (COVID-19) has brought several new questions to the forefront with respect to the design and operation of the buildings in which we spend much of our time, specifically when it comes to infection control.

Many of us are asking “how clean are our buildings, really?” and, “what can be done to control the spread of viruses in a high-density space?” Topics like surface cleaning and air purification practices that were once the sole domain of the health care industry are now top of mind in discussions about workplaces, restaurants, education facilities, retail spaces and grocery stores. With this renewed interest comes a new market for many high-quality sanitation and air filtration products — but separating the valid claims from the noise can be difficult.

HEPA filtration

High-Efficiency Particulate Air (HEPA) filters are most effective at removing small particles.

A standard air high-efficiency particulate air filter looks and acts much like any air filter in that it captures but does not kill contaminants. The HEPA designation means that the filter assembly was designed and tested to capture 99.7% of particles in the air passing through it that are 0.3 microns in size. The 0.3-micron size represents the most difficult particle size to capture so the 99.7% capture rate actually represents the worstcase efficiency of the filter. For particles that are larger or smaller than 0.3 microns, the capture rate increases.

Figure 1: High efficiency particulate air filters can be very effective in capturing and removing viruses from air streams, as long as they pass through the filter. Courtesy: Lance Schmittling/Henderson Engineers

Since most viruses are less than 0.3 microns, HEPA filters can be very effective in capturing and removing viruses from air streams. HEPA filters are typically installed in the ductwork and therefore must rely on the room airflow patterns to carry contaminants to the filter, small particles like viruses circulate in the room for an extended time before eventually making their way to the filter for capture. While highly effective and reliable, an in-duct HEPA filter is more appropriate

in preventing cross contamination between spaces.

Disadvantages:

• Only captures particles from the ducted air — not within the space.

• Some increase in energy usage due to increase air pressure drop and motor work.

• Increased maintenance due to filter replacement.

Advantages:

• Proven technology, no moving parts, easily retrofitted.

• Effective at particle entrapment.

• Effective at protecting space-to-space contamination.

Bipolar ionization

Bipolar ionization generators create positively and negatively charged oxygen ions which bind to contaminants in the indoor air, either causing them to drop out of circulation in the room or to be captured by a mechanical filter within an air handling unit. When properly installed, operated and maintained, bipolar ionization systems can reduce dust and mold, capture odors, reduce volatile organic compounds and reduce viruses and bacteria in the air.

Figure 2: Bipolar ionization generators create positively and negatively charged oxygen ions, which bind to contaminants in the indoor air. Courtesy: Lance Schmittling/Henderson Engineers

Ions generated by these devices typically have a relatively short life span, so it’s important to regularly pass room air over the ion generator to ensure sufficient contact. Typically, bipolar ionization generators are installed in the ductwork or directly in the air handling unit, but recirculating room units are available through some manufacturers

Disadvantages:

• Emitter wear and calibration requirements.

• Only captures particles from the ducted air — not within the space.

• Potential to create ozone byproduct.

Advantages

• Little additional pressure drop added to system.

• Requires no re-engineering of existing HVAC system.

Humidification

Pathogens and infectious droplets travel further in dry air, especially when the relative humidity is below 40%, which is partly why we tend to see more illness in the drier winter months. By maintaining indoor relative humidity between 40% to 60%, building operators can reduce the risk of spreading airborne infectious diseases in their facilities.

Disadvantages

• Does not capture or kill pathogens.

• Consumes water for humidification.

• Can add significant cost to the system installation.

Advantages:

• Creates a less hospitable building climate for viruses.

• Reduces static.

• Increases occupant comfort in winter.

Ultraviolet sterilization

Anyone who has ever gotten a sunburn is familiar with UV light’s ability to degrade organic materials. Given the proper contact time and intensity, UV light can inactivate viruses and bacteria — rendering them harmless. UV lights can be installed in an air handling unit or even directly in the space itself, but the light must directly contact the pathogen in order to be effective. There is no travel distance or “conditioning” of the air that takes place.

UV light, with a wavelength between 200 to 280 nanometers has proven to be the most effective for infection control while inflicting minimal damage to human skin or other mammals present in the space.

Disadvantage

• Does not filter contaminants from the space.

Advantages:

• Can destroy microorganisms like mold, bacteria and germs.

• Applicable in a room-based or air handlerbased setting.

Body temperature detection

One way to control the risk of infection in your facility is by detecting potentially contagious patrons before (or as) they walk through your doors. To do this, one widely discussed solution is the application of thermal imaging to detect body temperatures. These systems work by using infrared radiation to evaluate temperature differences on the surfaces of the skin or other materials. A variety of devices exist with this technology including ceiling/wall-mounted cameras, handheld thermal imagers or devices integrated into existing security or building automation systems. Standard can help to know details procedure.

In particular, the world's two top international standards groups, the IEC and ISO, have published 3 standards covering fever (i.e., febrile) screening:

• IEC 80601-2-59:2017 Medical electrical equipment — Part 2-59: Particular requirements for the basic safety and essential performance of screening thermographs for human febrile temperature screening
• ISO/TR 13154:2017 Medical electrical equipment — Deployment, implementation and operational guidelines for identifying febrile humans using a screening thermograph
• ISO 80601-2-56:2017 Medical electrical equipment — Part 2-56: Particular requirements for basic safety and essential performance of clinical thermometers for body temperature measurement

FDA Endorsed

Both organizations have published detailed standard guides for fever detecting thermal camera solutions, and the FDA has endorsed them, including in their most recent guidance stating:

cameras are tested and labeled consistent with the following standard: IEC 80601-2-59:2017

the camera's labeling references and is consistent with the guidelines in ISO/TR 13154: 2017

FDA considers body temp screening cams (paired with a thermometer to confirm the fever) to be medical devices, technically a "Telethermographic system intended for adjunctive diagnostic screening". These require FDA 510(k) clearance before being marketed, a process that takes around 130 days. On Apr 17, 2020 The US FDA has declared it will not go after the many companies marketing unapproved fever detection cameras during the coronavirus public health emergency, even though it does consider these products medical devices, it has announced 10 page new guidance ( Click to get enforcement policy). The FDA says that a 'prominent notice' should be included, explaining: The labeling includes a prominent notice that the measurement should not be solely or primarily relied upon to diagnose or exclude a diagnosis of COVID-19, or any other disease.

ISO give importance of the inner eye area is best real-life thermal cam images from the ISO/TR 13154:2017. thermal cam readings must use a blackbody.

The IEC also states to the OPERATOR to ensure that the FACE is unobstructed by hair, eyeglasses, and other objects because their presence will interfere with the ability of a SCREENING THERMOGRAPH to detect a febrile condition. Notably, ISO states a face mask is also an obstruction, and leads to warmer-than-usual readings due to warm breath exhalations being reflected back onto the face.

IEC states the minimum laboratory accuracy for a thermal camera including the measurement uncertainty shall be less than or equal to an offset error of ±0,5°Cover the range of at least 34°C to 39°C

IEC states face should be parallel to the camera shall accommodate a FACE that is positioned 0.75 m to 2.2 m above the floor. This requirement may be met by moving the infrared camera. The plane of the lens of the infrared camera also should be parallel to the FACE and in line with the TARGET.

IEC states cameras must be parallel in order to maximize the number of pixels in the face image, which should be a minimum 240 by 180.

Many of the manufacturers IPVM are using 400x400 (e.g., Sunell's Panda Cam) or smaller 320x288 sensors, which means they could only comply with this when reading a single face, not 10 or more in a row or the 40+ shown in marketing details.

The ISO/IEC standards make no mention of such AI or of anything else helping overcome these obstructions. This sets up an issue where manufacturers may argue these 2017 standards are out of date.

Some manufacturers have also touted "compensation algorithms" they claim automatically adjust for the (well-known) difference between face skin temperature and actual body temperature. However, the ISO recommends that this "small difference" between inner eye temp and body temp be accounted for by adjusting the "threshold temperature", i.e. the specific temperature at which the system alarms.

IEC says A high temp reading cannot be automatically considered a fever, and must be confirmed with a clinical thermometer, it should conform to a separate standard, ISO 80601-2-56.

The ISO/TR 13154:2017 and IEC 80601-2-59:2017 standards specifically state that fever screening is deployed under indoor conditions:

[IEC] screening thermographs have been used at ports-of-entry, ports-of exit and the entrances to buildings under indoor environmental conditions with the intention of separating febrile from afebrile individuals to help prevent the spread of communicable diseases

[ISO] this document provides general guidelines for the deployment, implementation and operation of a screening thermograph intended to be used for non-invasive febrile temperature screening of individuals under indoor environmental conditions to prevent the spread of infection.

IEC says the responsible organization needs to be aware of the type of lighting used at the screening area. Lighting such as incandescent, halogen, quartz tungsten halogen and other type of lamps that produce significant interference (heat) should be avoided. The area chosen for screening should have a non-reflective background and minimal reflected infrared radiation from the surroundings. IEC recommends A/C drafts be diffused to ensure they are not blowing onto people and cooling them. ISO adds that "sun-facing windows, radiant heaters, or sources of cold (cold windows or outside walls" can also "interfere" with accurate readings and must be avoided as well.

ISO states that Controlling ambient temperature is important, as overly hot/cold people will not give accurate results, particularly if they are sweating, “individuals being screened should not be too cold or too hot and especially not sweating”.

ISO states that the temperatures measured by a screening thermograph can be influenced when the individual being screened is sweating. Sweating thresholds can vary according to a person’s fitness level, environment of residence, length of adaptation and the relative humidity. When humidity is controlled, these effects are minimized. To produce consistent and reliable results of the temperature screening process, it is imperative that the screening thermograph be situated in a reserved stable indoor environment with a temperature range of 20 °C to 24 °C and relative humidity range from 10 % to 50 %.

ISO states one way to achieve such conditions would a be a special walk-through booth. In order to prevent "cross-contamination" (febrile individuals in the line infecting others), the ISO recommends that a "secondary screening area" be set up "removed from the general traffic flow" for people who are being confirmed for fever. The secondary screening area should be properly equipped with "masks, wipes, disinfectants”. The secondary screening area is a care area that should equipped with a clinical thermometer and accessories that comply with ISO 80601-2-56 and should be staffed by qualified medical personnel. The secondary screening area should be equipped with sanitation supplies, e.g. masks, wipes, disinfectants. To prevent cross-contamination, the secondary screening area should be positioned to allow patient removal from the facility or to quarantine with reasonable privacy and with minimum exposure to others (maintaining crosscontamination prevention).

ISO says bathrooms should not be near screening areas. Toilets should not be proximal to the screening thermograph area. This is to both inhibit potential cross-infection and to prevent facial washing (alteration of the thermal profile) immediately prior to entering the screening thermograph area.

ISO says the backdrop behind the individual being screened and, where utilized, side screens should be — thermally uniform, — non-reflective in the IR spectrum, and — not dark in colour in the visible spectrum (closer to white than black).

ISO recommends a single file line, and that people should "stop and pause". However, ISO does state that at high-volume situations, the system can operate in "near real time". To minimize disruption in high volume situations, the response time and throughput of the screening thermograph should be capable of operating in near real time for rapid and effective screening. This can necessitate that the screening thermograph be highly automated. But in low-volume scenarios, it's still best to ask people to stand still.

ISO recommends the responsible organization should retain this information(data) for at least one month (normal maximum incubation time for known infectious diseases). The responsible organization should be prepared to maintain the data for longer periods when deemed necessary by the public health authorities and other organizations ensuring protection of public safety.

Technically, the GDPR does not apply to thermal camera readings, as it only deals with the "processing of personal data" i.e. data that can identify a specific person - which thermal readings cannot.

Vaporized hydrogen peroxide injections

On the more aggressive end of the spectrum for room sterilization technologies is the injection of vaporized hydrogen peroxide directly into the space. Hydrogen peroxide is a potent sterilizing agent that has been used to decontaminate buildings infected with a range of biological contaminants from anthrax spores to exotic viruses. The process is performed by injecting vaporized hydrogen peroxide into a sealed vacant space and is usually used more as an intentional sterilization procedure rather than a routine part of normal building operation.

Disadvantages

• Requires pre-cleaning of all surfaces before disinfecting.

• Not practical for wide disinfection of occupied/finished spaces like office buildings or schools.

• Not for human use.

Advantage

• Highly effective at destroying microorganisms like mold, bacteria and germs.

As a society, our awareness of how quickly potential pathogens can spread has increased dramatically in just the span of a few months. We understand the importance of human health and furthermore, we understand that our economic livelihood as individuals, as a nation and even as a world depends greatly on our ability to move about freely without concern for the spread of infection.

Find more resources at

www.csemag.com

https://www.iso.org/standard/69346.html

https://www.iso.org/standard/69347.html

https://www.iso.org/standard/67348.html

https://ipvm.com/reports/fda-new