For the longest of times, facilities HVAC systems have relied on the air distribution systems to manage airflow around the facility. Positive pressure air flow is also for occupants to ensure a healthy, productive, and energy-efficient environment. Airflow also provides the critical area positive pressure spaces to remain sterile from pathogens. With a filtered, positive air pressure in a clean room, bacteria and other airborne contaminants (e.g., mold spores, viruses, and allergens) can be forced outside or into “dirtier” areas of the facility where air quality is not as critical.
Air distribution systems must be dynamic and capable of delivering air based on an operational demand rather than arbitrarily selected fixed volumes.
What is a Positive Pressure Room?
A positive air pressure means that the air inside the room is greater than the air outside of the room adjacent to it. It is achieved by pumping clean and filtered air, usually through the ceiling. A positive air pressure facility aims to keep any possible pathogens or contaminants out of the room or facility.
A positive air pressure facility must be well sealed. It should not allow the entrance of contaminated air to the room or facility. Instead, it only allows required cleaning and filters inside the facility. But in case of a door opening or any air leakage, the clean and filtered air is forced out of the facility rather than letting the unfiltered outdoor air enter.
Who Needs a Positive Pressure Facility?
Positive pressure facilities are used primarily in various industries where cleanliness and sterility are the prime concern. One of these is the microelectronic manufacturing industry. Microelectronic processing must avoid even the smallest particle. It can damage the integrity of the microchips being produced.
Another is the isolation room in hospital facilities. This room is intended for patients with weakened immune systems, cancer, or transplants. It is to ensure they are well protected from contaminants that could compromise their health and safety.
Hospital operating rooms and In Vitro Fertilization laboratory also use positive pressure. It is to ensure no impurity from the outside may enter the area. Another is the oil platform where flammable gases may exist.
The food manufacturing industry also uses positive pressure facilities. It is to ensure the whole operation is cleanest until it is well-sealed and packed. It protects the food against contaminants that could hamper production.
How to Create Positive Airflow?
The HVAC system air handling unit is responsible for creating positive airflow. In a large facility, the wind became the essential element in the rooftop venting airflow system. It helps circulate the airflow which could provide comfort to the staff.
In a critical facility, there are some ways to create positive airflow and keep clean areas as clean as possible. First, a facility must be scrutinized by HVAC experts. Experts understand airflow and have methods to quantify airflow patterns.
According to Mike Follmer, Hixson Architecture & Engineering vice president/project architect, the following are several factors in designing proper airflow in a new plant.
- What kind of product is made at the site?
- What will production volumes be handled?
- What risks are inherent with the product/process?
- What are the sanitation methods and protocols?
- What are the adjacent spaces, and how might they affect the area air handling system?
- What are the air pressurization requirements?
- What openings exist throughout the facility, and how might they affect the system?
It is essential to consider how the components in a building or facility need to work together. In any facility, the design zone of airflow depends on the product and production method. But most of all, the highest pressure should be in the cleanest room, and the lowest pressure is in the least clean. It must be essential to remember not to allow the entrance of unfiltered and contaminated air to a sterile environment.
According to Donna Lorenzen, The Austin Company’s chief mechanical engineer, “The primary consideration is to prevent air from flowing into the high-care areas from the low-risk areas. The level of filtration required can vary, depending on the final product and phase of production.”
In creating positive airflow, it is vital to have multiple systems rather than only a single system. It should allow the function of another system in case of an equipment failure or malfunction. Otherwise, a single air system for the whole facility would require a shutdown of the entire plant.
Multiple air systems work well in maintaining the correct room pressure. It also ensures efficient temperature, humidity, and filtration level. It also avoids cross-contamination, especially for the food manufacturing industry.
Tools to Test Positive Airflow System
“Spreadsheets for calculating pressure difference and airflow requirements are commonly used,” according to Frank Mangin, Haskell group vice president, AE services.
Though they vary according to function and application, design guidelines can assist in laying out the devices to ensure proper air filtration.
ASHRAE standards are one of the design guidelines that must be considered. It sets the required selection of appropriate air-moving and filtration equipment and configurations. It also considers the number of openings in the room to adjacent spaces and process exhaust.
Computational Fluid Dynamics (CFD) programs are also an essential tool in designing the airflow system. It is used to model a space thermodynamically.
There are also software tools that aim to create accurate size systems. It helps air handling units precisely hold the proper room temperature and humidity levels based on the size and climate of the space the unit is serving.
One of these is the LCC modeling software that accurately predicts the performance characteristics of almost any air filter on the market today.
In testing the positive directional airflow, visual tracer techniques use “smoke tubes” or handheld “fog generators.” Nevertheless, facilities aiming to put positive pressure on airflow should establish an infection control risk assessment.
Filtration vs Energy Use
HEPA filters with at least a MERV 13 filter are also necessary. It requires positive air to keep filtered, conditioned air within the space and unconditioned or unfiltered air from adjacent rooms. The lifetime of the filter must also be considered. The real-life average pressure drop, airflow, filtration efficiency, service life, and energy demands depend on the particular filters selected and used.
According to Haskell’s Mangin, “There are many filtration options, from the type of media used to efficiencies HEPA Filters and ease of maintenance (roll filters, pre-filters/final filters and a myriad of filter housings and locations that can affect labor costs for replacement).”
A separate filtration unit is effective in ensuring that the airflow needed for filtration is much higher than that required for temperature, heat, and pressure control. Tight spaces with different pressure and cleanliness requirement are ideal in reducing the possibility of cross-contamination.
Using lower velocity may reduce the filtration energy cost. The larger the cross-section, the lower the velocity. As a result, less energy is required to move air through each section. These sections can be a filter, cooling coil, gas furnace, and so on. However, it may have a higher installation cost.
“The best way to limit energy use is to make sure filters are changed based on the intervals specified by the filter and the equipment manufacturers. Also, it is imperative not to specify a filter that is overkill for the application. Keeping filter velocities as low as reasonably possible saves energy over the life of the unit because of the reduced air pressure drop.” says EVAPCO’s Sunnarborg.
There is a need for a higher-pressure drop filter in achieving a higher filtration level, and you’ll spend more energy to push air through it. A pressure differential gauges is an inexpensive tool for monitoring filters for replacement.
How to Maintain Clean Air
Maintaining clean air starts with essential and straightforward practice. There must be a practice in achieving clean surroundings in manufacturing plants. A critical space must establish a hygienic policy. Staff may use stringent uniforms, locker rooms, plant-issued footwear, and sanitary over-garments.
In various industries, vestibules and automatic doors are built. This addresses the issues caused by leaving the doors open. Sensors and alarms are also included in the HVAC system. It aims to alert the staff if doors are left open for longer than expected. Today, building automation systems are used in fixing air quality issues.
Air Quality Sensor
AKCP Wireless Air Quality Sensor is the best choice to detect and monitor the level the pathogens and VOC particles in the air. Positive pressure areas must be void of any contaminants. A sensor helps in early detection and alerting for necessary actions. Detection capacity for particles for size PM 0.5 TO PM10, the sensor also accurately measures the concentration level of the particles present in the air. The good thing is the sensor is wireless and powered with a long-lasting battery (up to 10 years). Up to 30 wireless sensors can be connected to one wireless gateway. The Wireless Tunnel Gateway (WTG) will transmit the data collected from sensors to an online platform. AKCP base units and attached sensors can be configured and monitored from AKCPro Server (APS). Base units communicate with the server through your wired local network (LAN) or wide area network (WAN). Remote sites with no wired network send data to the server through the cellular data network* via a VPN connection.
HVAC Maintenance Monitoring
Maintaining positive pressure in a facility requires a monitoring device. It ensures that the HVAC is working correctly. It provides the proper positive pressure is efficiently implemented. Otherwise, it could compromise the safety and sterility of the product.
AKCP Wireless differential air pressure monitors the AHUs for pressure differential to ensure adequate airflow. Air Pressure Differential Sensors is utilized in hospitals or clean rooms where positive pressures are maintained inside rooms to keep them clean, or negative pressures to contain contaminants. Just like the wireless air quality sensor, it also works with all Wireless Tunnel™ Gateway.