Blog Tag: negative pressure

The word negative is always associated with something bad or the lack of something good. It is the opposite of the word positive.

In the world of minimizing contact with harmful airborne contaminants the word negative is often used in conjunction with negative air pressure, or making a specific room or area negative.

Hospitals have rooms where they isolate a patient that has a highly communicable disease where the air in the room is constantly being filtered through a HEPA based air filtration system and air handler. The pressure in the room is slightly lower than the air outside the room so when the door to the room is opened all the air moves into the room thus keeping any airborne pathogens from escaping the room.

Negative pressure rooms are common at the CDC in Atlanta and in R&D labs around the world where highly toxic or corrosive chemicals and materials are used for product development. These rooms use both HEPA and Carbon or other adsorptive materials to remove airborne particulate as well as gaseous pollutants.

Pure Air Systems, based in Indianapolis, Indiana manufactures high end, commercial grade HEPA and Carbon based, fan-powered air filtration systems which are used in many of these negative room applications. Their systems can move from 50 CFM up to 2,000 CFM of air through the scanned HEPA filters where in many cases the units themselves are the only air moving device creating the negative pressure.

These systems can also be attached to or be part of the air handling units working in conjunction with cooling and heating systems.

In many instances homes can be under negative pressure when the HVAC system is not properly balanced making the home slightly negative which in this case is bad. That means every time the air handler fan comes on the house tends to draw some air in from the outside which means you are bringing in warm, moist or cold air all the time. Getting your HVAC systems balanced is recommended.

For more information on the complete line of HEPA and Carbon based air filtration systems please go to our website at: https://www.pureairsystems.com or call us on our toll-free number at: 800-869-8025.

Pure Air Systems started making HEPA based air filtration systems in 1985. Today they are one of the leaders in HEPA filter technology with over 7 different fan powered systems ranging in capacity from 50 CFM to 2,000 CFM.

In the 60’s and 70’s Asbestos removal was a very big industry as older homes and builders were gutted to remove the harmful asbestos materials. In order to keep the asbestos fibers from flying around and getting out into the open areas or outside the contaminated space, the areas being cleaned up were enclosed in 3 millimeter thick Polyethylene sheeting. Large, fan powered HEPA systems were placed outside the containment area pulling air from inside the containment area creating a negative pressure inside the cleaning zone.

The HEPA filters would trap any of the Asbestos particles and when you entered the containment area through a zipped door air would move into the zone rather than come out of the zoned area.

In the medical field when patients are considered to have a highly communicable disease, they are often placed in rooms that are kept under negative pressure again using fan powered HEPA filter systems. This ensures that any viruses in the room stay in the room.

These same techniques are used by the CDC or WHO when they are working with deadly viruses and bacteria. The rooms where they experiment with these pathogens are tightly sealed and under negative pressure with the air passing through multiple layers of HEPA filters using HEPA, ULPA and SULPA filters. The rooms are designed so that the doors will not open unless the air handlers and HEPA systems are in operation.

HEPA filters are made from very dense media and they have a lot of resistance so larger motor /blower units are required to move air through the HEPA filters. HEPA filters are the only filters capable of removing particles as small as 0.12 microns at levels approaching 99.99995%.

For more information on the complete line of HEPA filters please go to our website at: https://www.pureairsystems.com or call us on our toll-free number at: 800-869-8025.

You always hear about the eternal optimist that says you can always turn a negative into a positive if you just rethink the problem. All too often we have something happen in our lives that creates a negative feeling or puts us in a negative mood. But these negative thoughts are a waste of energy. Instead of dwelling on what could go wrong or did go wrong, look at all the positive things in you life and don’t waste energy worrying about the negative aspects of the issue.

The title of this blog relates to turning two negatives into a positive and while your life  maybe filled with multiple negative thoughts the two negatives I am referring to relate to negative pressure of the physics kind.

Pure Air Systems has been making HEPA and Carbon based, fan powered, commercial grade air filtration systems since 1985. The use of certified, commercial grade HEPA filters creates a design issue in how you incorporate the motor/blower assembly and HEPA filter to obtain maximum performance with minimal noise and air turbulence.

HEPA filters, by their nature, have a relatively high resistance to air flow due to the extremely dense HEPA paper that is used in the fabrication of the filter. When moving air through a fan/motor assembly with a HEPA filter in line you have two options. You can put the fan in front of the HEPA and blow air through the HEPA filter keeping the fan/motor assembly in the dirty air stream or place the HEPA in front of the fan/motor assembly.

Since the resistance to moving air across the HEPA is so high ( over 1.0 inches as measured in water column) pushing the air through the HEPA filter creates an air buffeting affect and requires more horsepower to push the air through the filter. By placing the fan/motor assembly on the clean air side or “negative” side of the HEPA you get a very smooth flow of air, little or no buffeting and a reduction in horsepower requirements.

The HEPA systems manufactured by Pure Air Systems also incorporate a carbon media filter and a polyester, dual layer ring panel roughing filter. All of these filters are placed ahead of the fan/motor assembly. So they are all on the negative side of the blower and offer the same benefit of having a smooth, non-buffeting air flow across their surface areas and keep the blower and motor clean. So in essence, you are turning three negatives into a positive.

Many other companies that utilize HEPA filters in their systems place their blower/motor assembly ahead of the HEPA and this creates more noise fills up the HEPA filter faster as it tends to push the dirt into the HEPA paper rather than pull the dirt through, which is a more efficient way of using the HEPA filter.

For more information on this aspect of the HEPA systems made by Pure Air Systems please go to our website at: www.pureairsystems.com

In the health care, micro-electronics, micro-chip manufacturing, optics, food processing and other environmentally sensitive applications, the need for high end air filtration or HEPA filtration is high.For example, all hospital and out-patient surgery suites require 100% HEPA filtered air all the time whenever a patient is in surgery.

However, did you know that not only does the surgery room require HEPA filtration but it must operated under a negative pressure system?

The concept of negative and positive air pressure as a means to control an enclosed environment has been around for a long time. While we don’t always notice it, we all see this working on a day-to-day basis in the everyday world.

Remember the last time you opened the door to an office building and you had to pull real hard to get the door to open. Or, just the opposite. You opened the door to a building and when it opened up it blew your hair back. The first example is negative pressure, the second positive pressure.

A building or any enclosed room or structure can become negative when the air handling (heating/cooling) system has a design flaw where more return air is being pulled to the air handler than supply air.

This can happen mechanically for a number of reasons but suffice it to say that when this in-balance of air occurs any opening, crack, or communication point in the structure will draw in air, dust, dirt and any small airborne particulate from the outside or an adjoining space.

The opposite in-balance can also occur where there is more supply air than return air creating a positive pressure environment. In this case the room or enclosure maintains a much cleaner environment since the positive pressure prevents any outside contaminants from entering the room.

For applications such as surgery rooms and micro-chip manufacturing, the rooms must not only be HEPA filtered but be under constant positive pressure.

When a patient is in surgery and the body cavity is open the possibility for infection from any airborne pathogen is extreme. Even with all the air being HEPA filtered, if the room itself was not under positive pressure the ability for small, sub-micron contaminants to enter the room is great.

Micro-chip manufacturing has a similar problem. The micro-chips are actually layers upon layers of silica and if even a tiny, sub-micron particle falls in between the layers, the chip is ruined. Again, positive pressure is required in this application.

In applications where a harmful contaminants, highly infectious bacteria and viruses or harmful gases are present, negative pressure systems are applied to keep the contaminants from leaving the room or enclosed area.

Pure Air Systems HEPA filtration units are powerful and can be used to make a room negative or positive by themselves. They can also be used in conjunction with any HVAC system to accomplish this goal. The ability to both provide HEPA filtered air and produce the desired pressure in the room for the specific application make these systems unique in the market place today.

For more information on positive and negative pressure and the overall capabilities of the HEPA systems go to: www.pureairsystems.com