Ac monitoring guidelines -
Three CADR numbers are given on the AHAM label, one each for smoke, dust, and pollen. The smoke particles are the smallest, so that CADR number applies best to viral particles related to COVID and other viral respiratory diseases. The label also shows the largest room size in square feet [ft 2 ] that the unit is appropriate for, assuming a standard ceiling height of up to 8 feet.
If the ceiling height is taller, multiply the room size ft 2 by the ratio of the actual ceiling height ft divided by 8. The CADR program is designed to rate the performance of smaller room air cleaners typical for use in homes and offices.
For larger air cleaners, and for smaller air cleaners whose manufacturers choose not to participate in the AHAM CADR program, select a HEPA unit based on the suggested room size ft 2 or the reported air flow rate cfm provided by the manufacturer.
Consumers might take into consideration that these values often reflect ideal conditions which overestimate actual performance. For air cleaners that provide a suggested room size, the adjustment for rooms taller than 8 feet is the same as presented above. If the ceiling height is taller, do the same calculation and then multiply the result by the ratio of the actual ceiling height ft divided by 8.
Using ductwork and placing the HEPA system strategically in the space can help provide desired clean-to-less-clean airflow patterns where needed. Example 2. Solution: The addition of the HEPA filter device provides additional clean air to the room.
Thus, the increased ACH and lower k value associated with the portable HEPA filtration unit reduced the wait time from the original 5 hours and 45 minutes to only 1 hour and 24 minutes, saving a total of 4 hours and 21 minutes before the room could be safely reoccupied.
Adding the portable HEPA unit increased the equivalent ventilation rate and improved room air mixing. Yes, when an appropriate dose of UVGI is applied.
Ultraviolet germicidal irradiation UVGI , otherwise known as germicidal ultraviolet GUV , is an air and surface treatment tool used in many different settings, such as residential, commercial, educational, and healthcare settings.
The technology uses ultraviolet UV energy to inactivate kill microorganisms, including viruses, when designed and installed correctly. UVGI can inactivate viruses in the air and on surfaces.
Seek consultation with a reputable UVGI manufacturer or an experienced UVGI system designer prior to installing UVGI systems. These professionals can assist by properly designing, installing, and commissioning the system for your specific setting. In addition, the site where the product is manufactured may also require registration.
Upper-room UVGI Upper-room or upper-air UVGI uses specially designed UVGI fixtures mounted on walls or ceilings to create a treatment zone of ultraviolet UV energy that is focused up and away from people.
These fixtures treat air as it circulates from mechanical ventilation, ceiling fans, or natural air movement. The advantage of upper-room UVGI is that it treats the air closer to and above people who are in the room.
Since the s, UVGI systems have been widely used for control of tuberculosis TB. The CDC guidance Environmental Control for Tuberculosis: Basic Upper-Room Ultraviolet Germicidal Irradiation Guidelines for Healthcare Settings provides information on appropriate UVGI system design, related safe operation, and maintenance.
Based on data from other human coronaviruses, a UVGI system designed to protect against the spread of TB should be effective at inactivating SARS-CoV-2 and therefore prevent spread.
While small spaces may require a single UVGI fixture, most UVGI systems usually require multiple UV fixtures to be effective. For example, a rectangular-shaped waiting room with 10—30 occupants will require 2—3 upper-air UVGI fixtures.
As part of system installation, care must be taken to control the amount of UV energy directed or reflected into the lower occupied space. Reputable UVGI manufacturers or experienced UVGI system designers will take the necessary measurements and make any required adjustments to prevent harmful UV exposures to people in the space.
Potential Application: Can be used as an additional layer of protection to treat the air kill germs in indoor spaces; most useful in spaces that host large gatherings or where the risk of disease transmission is high. In-duct UVGI In-duct UVGI systems are installed within a heating, ventilation, and air conditioning HVAC system.
These systems are designed to serve one of two purposes:. These devices produce relatively low levels of UV energy. This energy is continually delivered 24 hours a day, which is why they are effective. Coil treatment UVGI devices are not designed for treating the air and should not be installed for this purpose.
Potential Application: Can be used to reduce HVAC maintenance and improve operational efficiency within large, commercial HVAC systems or residential HVAC systems; not recommended for inactivating airborne pathogens.
HVAC air treatment UVGI systems generally require more powerful UV lamps or a greater number of lamps, or both, to provide the necessary UVGI required to inactivate pathogens in a short period of time. Air treatment systems are often placed immediately downstream of the HVAC coils. This location keeps the coil, drain pan, and wetted surfaces free of microbial growth and also treats the moving air.
Potential Application: Can be used inside any HVAC system to reduce the concentration of infectious airborne pathogens. Whole-room UVGI Whole-room UVGI commonly referred to as Far-UV uses specially designed UVGI fixtures mounted on walls or ceilings to create a treatment zone of ultraviolet UV energy that extends throughout an occupied space.
While standard UVGI fixtures emit UV energy at a wavelength around nanometers nm , far-UV devices use different lamps to emit UV energy at a wavelength around nm. Aside from the wavelength, a major difference between the two technologies is that standard UVGI systems are generally designed to avoid exposing people to the UV energy, while many far-UV devices are marketed as safe for exposing people and their direct environment to UV energy.
Recent research has indicated nm energy is much safer for humans than once thought. In fact, the American Conference of Governmental Industrial Hygienists ACGIH recently increased their Threshold Limit Values TLVs 7-fold for eyes and over fold for skin exposed to nm energy.
This increase was in response to data showing nm energy does not penetrate the tear layer of the eye or the layer of dead skin stratum corneum that protect living skin beneath. Research studies also indicate that far-UV wavelengths can effectively inactivate microorganisms, including human coronaviruses, when appropriate UV doses are applied under experimental conditions.
However, there are still some questions about how effective nm energy can be in real occupied spaces against human-generated pathogens when UV exposures are controlled to safe limits. Far-UV is a promising technology that may well prove to be effective at treating air and surfaces, without some of the safety precautions required for standard UVGI.
Due to the potential promise this technology represents, there are substantial private and public research activities underway to further validate claims of safety and efficacy. In the near term, whole-room UVGI is best viewed as new and emerging technology.
Consumers considering an emerging technology such as Far-UV should read FAQ 8 on emerging technologies below. Potential Application : Air and surface treatment in occupied indoor environments.
CDC recommends using technologies that are known to work and will not cause harm. Be cautious when considering an emerging new technology.
Do your homework, to include requesting proof of performance and safety under real-world, as-used conditions. CDC does not provide recommendations for, or against, any manufacturer or product.
There are numerous technologies being heavily marketed to provide air treatment during the ongoing COVID pandemic. Common among these are ionization, dry hydrogen peroxide, and chemical fogging.
Some products on the market include combinations of these technologies. These products generate ions, reactive oxidative species ROS, which are marketed using many names , or chemicals into the air as part of the air treatment process.
People in spaces treated by these products are also exposed to these ions, ROS, or chemicals. Some research has found these exposures may be harmful under certain conditions, including high concentrations or vulnerable populations. While variations of these technologies have been around for decades, relative to other air cleaning or treatment methods, they have a less-documented track record when it comes to treating large and fast volumes of moving air within heating, ventilation, and air conditioning HVAC systems or even inside individual rooms.
This does not necessarily imply the technologies do not work as advertised. As with all emerging technologies, consumers are encouraged to exercise caution and to do their homework.
Consumers should research the technology, attempting to match any specific claims against the intended use of the product. Consumers should request testing data that quantitively demonstrates a clear protective benefit and occupant safety under conditions consistent with the intended use.
When considering air treatment technologies that potentially or intentionally expose building occupants, the safety data should be applicable to all occupants, including those with health conditions that could be aggravated by the air treatment.
In transient spaces, where average exposures to the public may be temporary, it is important to also consider occupational exposures for workers that must spend prolonged periods in the space.
Preferably, the documented performance data under as-used conditions should be available from multiple sources, some of which should be independent, third-party sources. Unsubstantiated claims of performance or limited case studies with only one device in one room and no reference controls should be questioned.
At a minimum, when considering the acquisition and use of products with technology that may generate ozone a gas with potentially harmful health effects , verify that the equipment meets UL standard certification Environmental Claim Validation Procedure ECVP for Zero Ozone Emissions from Air Cleaners which is intended to validate that no ozone is produced.
Yes, carbon dioxide CO 2 monitoring can provide information on ventilation in a given space, which can be used to enhance protection against COVID transmission. Strategies incorporating CO 2 monitors range in cost and complexity.
However, greater cost and complexity does not always mean greater protection. Limited information exists regarding a direct link associating CO 2 concentration to a risk of COVID transmission. Changes in CO 2 concentrations can indicate a change in room occupancy and be used to adjust the amount of outdoor air delivered.
However, CO 2 concentrations cannot predict who has COVID infection and might be spreading the virus, the amount of airborne viral particles produced by infected people, or whether the HVAC system is effective at diluting and removing viral concentrations near their point of generation.
Ventilation based on CO 2 measurements cannot recognize the increased risk of transmission when multiple room occupants are infected. In some well-designed, well-characterized, well-maintained HVAC environments, the use of fixed CO 2 monitors can be informative.
When used, these monitors are often incorporated into demand-controlled ventilation DCV systems that are designed with a primary intent of maximizing energy efficiency through reductions in outdoor air delivery. However, during times of high community transmission, guidance is often to deactivate DCV systems and exceed minimum ventilation whenever possible, in addition to enhanced filtration, and other intervention-focused considerations.
Traditionally, CO 2 monitoring systems are expensive, require extensive knowledge to accurately install and set up, and require sophisticated control programs to effectively interact with the building heating, ventilation and air conditioning HVAC systems in real time.
They were not designed to protect building occupants from disease transmission. Fixed-position CO 2 monitors measure CO 2 concentration as an indicator of the number of people in the space. As the CO 2 concentration increases, the HVAC DCV system increases the amount of outdoor air ventilation in the space to dilute CO 2 and vice versa.
The number of CO 2 sensors, the placement of those sensors, and their calibration and maintenance are collectively a large and complex issue that must not be overlooked.
For example, the CO 2 concentration measured by a fixed, wall-mounted monitor may not always represent the actual concentrations in the occupied space. If air currents from the room HVAC, or even make-up air from windows, flows directly over this monitor location, the corresponding concentration measurements will be artificially low.
If the room has good air mixing, the measured concentration should approximate the true concentration, but rooms are rarely well mixed, particularly in older buildings with aging ventilation systems or none at all. This may result in elevated CO 2 concentrations in those other spaces which the HVAC system is unable to control.
A more modest, cost-efficient, and accurate use of CO 2 monitoring is the use of portable instruments combined with HVAC systems that do not have modulating setpoints based on CO 2 concentrations.
It is critical to select calibrated CO 2 meters whose sensors are reliable and accurate to draw meaningful inferences from measured indoor CO 2 concentrations. Under this approach, validate that the HVAC system is operating appropriately and is meeting or exceeding code-minimum outdoor air requirements based on current use and occupancy.
Next, measure the resulting CO 2 concentrations in rooms under as-used conditions using a handheld portable CO 2 meter. These observations will be the CO 2 baseline concentrations for each room under the HVAC operating conditions and occupancy levels.
One potential target for the baseline concentrations that is used to represent good ventilation is CO 2 readings below parts per million ppm. It is important to note, however, that a single concentration value may not be an appropriate target for all space types and occupancies for the purposes of assessing the ventilation rate see ASHRAE Position Document on Indoor Carbon Dioxide.
Once a target concentration is identified, compare your baseline concentrations to the target concentration. If a baseline measurement is above the target, reevaluate the context under which the measurement was obtained and if warranted, investigate the ability to increase outdoor air delivery.
If unable to get below your target CO 2 value, increased reliance on enhanced air filtration including in-room HEPA air cleaners may be necessary. Once the baseline concentrations are established, take periodic measurements in each space and compare those to the initial baselines.
Generally, no. Temperature and humidity can both influence the transmission of infectious diseases, including COVID, but that influence has practical limitations in occupied spaces of buildings.
Research on the impact of temperature has shown that SARS-CoV-2, the virus that causes COVID, is sensitive to elevated temperatures, with over However, this temperature is far outside the limits of human comfort and could damage some building materials.
While temperatures lower than 70°C °F are also effective, the required exposure time for inactivation increases as the temperature decreases. So, elevated temperatures offer the potential for decontamination of SARS-CoV-2 virus in the air or on surfaces, but the use of increased temperature solely for decontamination is not generally recommended and is not realistic for occupied spaces.
Based on current evidence, it is not clear whether, in practice, increasing humidity could significantly reduce transmission of COVID beyond the reductions that result from using good ventilation and filtration.
Several scientific research studies have concluded that influenza and SARS-CoV-2 viruses do not survive as well in environments with higher humidity compared with lower humidity.
However, the reasons for this are unclear, and artificial experimental factors like the size of the liquid droplets used in the experiments and the composition of the liquid containing the viruses affect the results.
Thus, there is still debate within the scientific community over how much humidity affects virus survival outside of the laboratory. Adding humidity to indoor environments, especially in very cold climates, can also introduce additional challenges to the building environment.
CDC and standards-setting organizations like ASHRAE do not make recommendations about controlling indoor humidity to reduce virus survival, although humidity recommendations are made for other reasons, such as prevention of dust mite and mold growth or reduction of static electricity.
While fans alone cannot make up for a lack of outdoor air, fans can be used to increase the effectiveness of open windows, as described in the CDC list of ventilation mitigation strategies.
Fans can also be used indoors to improve room air mixing. Improved room air mixing helps distribute supplied clean air and dilute viral particle concentrations throughout the room, which reduces the likelihood of stagnant air pockets where viral concentrations can accumulate.
As with all fan use during the COVID pandemic, take care to minimize the potential to create air patterns that flow directly across one person onto another:. Fans can also enable clean-to-less-clean directional airflow.
Such applications should be evaluated closely to avoid unintended consequences and only adopted when supported by a safety risk assessment. Barriers can physically separate spaces that are next to each other.
When used for infection control, the barrier is intended to prevent someone on one side of the barrier from exposing a person on the other side of the barrier to infectious fluids, droplets, and particles.
Whether a barrier interferes with improved ventilation depends on how it is installed. Protective barriers can sometimes help improve ventilation, but they can sometimes hinder ventilation too. Sometimes they have no effect on ventilation.
Protective barriers can assist with improved ventilation when used to facilitate directional airflows or desired pressure differentials between clean and less-clean spaces. The barrier can be aligned with the intended airflow to help direct it towards a desired location, such as an HVAC return air grille or an in-room HEPA air cleaner inlet.
Example scenarios for this type of barrier deployment include those where there is a known source of potentially infectious aerosols, such as a dental operatory or COVID testing station.
Alternatively, the barrier might be placed between two areas to better isolate one side of the barrier from the other. In this configuration, the barrier can also assist the HVAC design scheme in establishing a desired pressure differential between the adjacent spaces.
It fights the damaging effects of an outside climate that may be too hot, too cold, too humid, or sometimes even not humid enough. It also keeps the build-up of heat from your racks of computer equipment in check. If your HVAC goes down, it generally isn't long before you'll encounter several serious problems that can take down a good portion of your network.
This is where an RTU remote telemetry unit or remote terminal unit comes in. Component of SCADA systems, this electronic device monitors your HVAC for failures. This happens both directly most HVAC units will self-report at least a few different types of failures by latching a relay contact and indirectly monitoring the temperature and humidity ranges that the HVAC system controls.
An RTU can also monitor many other pieces of gear simultaneously. A complete discussion of this monitoring device is outside the scope of this article, but you do need to realize that your HVAC remote monitoring needs must justify only a small fraction of an RTU purchase.
You're going to get a lot of other value out of a deployed RTU. How big should an RTU be to monitor your HVAC? As described above, your choice is dependent on other things at the remote site that must be monitored. However, if we assume for a moment that you only had to monitor HVAC, we can list the important elements for monitoring just that equipment.
You can then add to the spec for any other equipment that must be monitored. Most HVAC units will output alarms via relay contacts. At a minimum, you'll need a few discrete contact closure inputs to accept these alarms at your RTU. While there is an ongoing debate about the wisdom of using insulation materials in duct systems that might retain moisture longer, all sides agree that extraordinary attention to preventing moisture contamination of the duct work should be the primary strategy for preventing mold growth.
As a secondary strategy, designers should consider methods of reducing the potential for future problems to occur due to unforeseen moisture contamination by investigating insulation products now on the market that minimize the potential for moisture to penetrate the insulation material.
These include foil vapor retarders, tightly bonded non-woven vapor retarders, butt or shiplap edges and other techniques that have been developed by insulation manufacturers to address concerns about moisture. Nearly all schools currently use the mixed-airflow method for distribution and dilution of the air within the occupied space.
Designers should investigate a method called vertical displacement ventilation or thermal displacement ventilation. This approach successfully uses natural convection forces to reduce fan energy and carefully lift air contaminants up and away from the breathing zone. Quick removal of concentrated air contaminants and building pressurization are two ways that exhaust systems affect IAQ.
These areas should be maintained under negative pressure relative to adjacent spaces. Ensure that all system components, including air handling units, controls and exhaust fans are easily accessible.
To help ensure that proper operation and maintenance of HVAC system components will be performed, it is critical that the designer makes the components easily accessible. AHUs, controls and exhaust fans should not require a ladder, the removal of ceiling tiles, or crawling to gain access.
Rooftop equipment should be accessible by way of stairs and a full-sized door, not a fixed ladder and a hatch. Label HVAC system components to facilitate operations and maintenance. Labeling of HVAC components is an inexpensive and effective method for helping facilities personnel properly operate and maintain the HVAC systems.
The labels should be easy to read when standing next to the equipment and durable to match the life of the equipment to which they are attached.
At a minimum, the following components should be labeled in each ventilation zone of the school and should correspond with the HVAC diagrams and drawings. Building commissioning is a quality assurance program that is intended to show that the building is constructed and performs as designed.
Find more information on commissioning HVAC and other building systems. Skip to main content. Indoor Air Quality in Schools. Contact Us. Heating, Ventilation and Air-Conditioning Systems, Part of Indoor Air Quality Design Tools for Schools.
On this page: Codes and Standards Potential for Natural Ventilation and Operable Windows Selection of HVAC Equipment Energy Recovery Ventilation Location of Outdoor Air Intakes and Exhaust Outdoor Air Quantity Air Filtration Filter Efficiency Pressure Drop Monitoring Pressure Air Cleaning for Gaseous Contaminants Ventilation Controls Volume Monitoring and Control Moisture and Humidity Control Air Distribution Types of Air Distribution Exhaust Air Designing for Efficient Operations and Maintenance Commissioning References and Resources Codes and Standards The national consensus standard for outside air ventilation is ASHRAE Standard Design in accordance with ASHRAE standards Design systems to provide outdoor air ventilation in accord with ASHRAE Standard Ensure familiarity with and adherence to, all state and local building codes and standards.
Standards are available at ASHRAE. Potential for Natural Ventilation and Operable Windows In some parts of the country, where temperature and humidity levels permit, natural ventilation through operable windows can be an effective and energy-efficient way to supplement HVAC systems to provide outside air ventilation, cooling and thermal comfort when conditions permit e.
Designers should consider the use of natural ventilation and operable windows to supplement mechanical ventilation. Consider outdoor sources of pollutants including building exhausts and vehicle traffic and noise when determining if and where to provide operable windows.
If operable windows will be used to supplement the HVAC system, ensure that: Openings for outdoor air are located between feet from the floor head height ; Windows are adjustable and can close tightly and securely; and Windows are placed to take maximum advantage of wind direction, with openings on opposite sides of the building to maximize cross-ventilation.
Selection of HVAC Equipment In most parts of the country, climatic conditions require that outdoor air must be heated and cooled to provide acceptable thermal comfort for building occupants, requiring the addition of HVAC systems.
The selection of equipment for heating, cooling and ventilating the school building is a complex design decision that must balance a great many factors, including: Heating and cooling needs; Energy efficiency; Humidity control; Potential for natural ventilation; Adherence to codes and standards; Outdoor air quantity and quality; IAQ; and Cost.
Central air handling units have a number of advantages as compared to unit ventilators and heat pumps serving individual rooms, including: Quieter and therefore more likely to be turned on or left on by teachers and staff; Less drafty due to multiple supplies and a return that is away from occupants; Better at controlling humidity and condensed moisture drainage; Easier to maintain due to reduced number of components and few units to access; More space around units and can be accessed without interfering with class activities; Space for higher efficiency air filters and more surface area; Made of heavier duty components; and Less likely to have quantity of outdoor air supply inadvertently reduced.
Specify the following features for all air handling units. Double-Sloped Drain Pan and Drain Trap Depth Double-sloped drain pan - A double-sloped pan prevents water from standing and stagnating in the pan.
Non-corroding drain pan - Made from stainless steel or plastic. Prevents corrosion that would cause water to leak inside the AHU. Easy access doors - All access doors are hinged and use quick release latches that do not require tools to open.
Easy access to filters, drain pans and cooling coils is imperative. Double wall cabinet - The inner wall protects the insulation from moisture and mechanical damage, increases sound dampening and is easier to clean. Tightly sealed cabinet - Small yet continuous air leaks in and out of the AHU cabinet can affect IAQ and energy.
The greatest pressure differentials driving leaks occur at the AHU. Double wall doors with gaskets - Double wall doors provide better thermal and acoustic insulation and will remain flatter, allowing a better seal against door frame gaskets Minimum 2 inch thick filter slots - For better protection of the indoor environment, as well as the equipment and ducts, the filters slots should be able to accommodate 2 in.
or thicker filters.
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