Misting Booth FAQs
Why don't I just build my own misting booth?
What is the difference between an AEC Misting Booth and a Fogging Booth?
Where and when are AEC Misting Booths used?
What is the difference between an AEC Misting Booth and a Decontamination Shower?
Can I use the AEC Misting Booth as a Decontamination Booth?
Can I integrate the AEC Misting Booth with a different company’s modular wall system?
Why not use an Air Shower to clean the operator of powder before degowning?
Can a solution other than water be used in the AEC Misting Booth?
What to do with the waste water?
What type of performance testing was conducted on the AEC Misting Booth?
The Misting Booth is a contamination control device for the respiratory protection from inhalation hazards to the operator during the degowning process. When the occupant removes his/her protective clothing (PPE) he also removes his/her primary personnel protection (respirator). The misting booth is used to reduce the possible re-suspension of the particulate in the operators breathing zone. By virtue of what the misting booth is doing, it also reduces contamination into the degowning area. The misting booth works by gently wetting the surface of an operator’s protective gown with a fine water mist, causing the powder to stick to the surface instead of becoming airborne.
For the equipment to be effective the operator must follow correct misting procedures and the facility’s degowning procedure.
Effectiveness of the misting booth at wetting particulate is dependent upon misting cycle duration time, the physical and chemical properties of the particulates, operator technique while misting and on the material and design on the protective garments.
Why don't I just build my own misting booth?
- Relocate and reuse the misting booth: 100% reusable components. The AEC misting booths are completely modular. The knock-down construction allows for the ability to disassemble the booth and relocate it. This feature benefits small firms with leases because the modular booth always remains their asset, and when it is time to move, the modular booth can go with them. This feature also benefits the larger companies. Should their needs change and the modular booth would be better suited elsewhere, it can be moved without losing their original investment. The AEC Misting Booth‘s door and wall panels are interchangeable, allowing for straight though and 90° orientation options.
- Stronger, cleaner construction, suited for a pharmaceutical environment: Many booths today are built using drywall and studs or cinderblock construction, leaving unsupported cavities that can be easily punctured and rough surfaces that create crud traps. This construction requires sealing off areas and detailed cleaning due to all the dust generated by sawing, drilling, mortar, taping, sanding and painting. The AEC Modular Misting Booth is prefabricated with bolt on assembly. Once built, the booth can be fully washed and wiped down, including the ceiling, without leakage or water absorption concerns. The 304 SS construction materials are suitable for long life in a wet environment. There is no warping and no need for contact painting due to high humidity levels that would be attributed to conventional construction. The free standing booth supports its weight without structural reliance and tie-in to the existing structure.
- Faster installation so you can get back to business:The Misting Booth can be rapidly installed and commissioned in one day with simple push to connect plumbing and electrical harness connections. The speedy installation minimizes plant disruptions, compared to conventional construction (sub-contractors and several trades like glazers, painters, carpenters, plumbers, electricians, controls engineers, etc.) that can take weeks. Conventional construction can put any company behind schedule and this can translate directly into money lost. The faster you are back to normal, the faster you get back to business.
- Reduced engineering, architectural and permit fees: Our project package provides for the detailed CAD layout design, assembly drawings, P&IDs and bill of materials. Each project is assigned to an AEC project manager who will work with you from the project scope and requirements, to field commissioning and training. The misting booth is pre-engineered and can meet any building code. At most you may be required to have an engineer or architect review and seal our drawings, which is much less expensive than conventional construction from scratch. Furthermore, our modular misting booth can usually be assembled within a plant without a permit. This is never the case with conventional construction, which always requires a permit and may tie up a project for weeks.
- Quality and performance: AEC Misting booths are manufactured to exact standards and are inspected for quality before they ship. The finished product is never questionable, a clear point that conventional construction cannot make. How good is conventional construction? It depends on the work crew. The truth is that most construction, if not closely watched, can turn into a disaster. A buyer must always be on the watch for shortcuts and substandard work. This is never the case with the AEC products. In addition to the construction problems, conventionally constructed misting booths often have poor or insufficient mist coverage, which may cause oversaturation of some parts of the outer protective suit and under saturation for harder to reach parts. During commissioning of the AEC booth, a detailed Site Acceptance Check list is included to ensure the booth operates perfectly, which in turn, will ensure the containment performance of this proven design.
- Cost: AEC misting booths always costs less than conventionally constructed booths. Add to this the other benefits previously listed along with the accelerated depreciation allowed for modular construction (as illustrated below) and you will see why the popularity of the AEC modular Misting Booth has grown tremendously. This is why many companies no longer consider conventional construction for their modular misting booth needs.
- Tax Deductions: The AEC Misting Booth qualifies for the Section 179 Tax Deduction.
- Construction depreciation: With regards to depreciation and its classification, a modular Misting Booth system is considered equipment and depreciates accordingly. This is because the AEC Misting Booth can be fully dismantled, relocated and re-assembled, which grants the classification as tangible property with a 7 year accelerated depreciation life. Conventional construction becomes a permanent structural addition to the building, and is classified as real property with a 39 year, straight line depreciation life.
- How does this advantage affect the cost in the long run?
Assumptions (please consult this matter with your company’s accountant):- Maximum federal corporate tax of 35%.
- AEC Misting Booth qualifies for 7 year depreciation, yearly write off is 14.3% (1/7 project cost).
- Conventional construction depreciation is 39 years, yearly write off is 2.6% (1/39).
- After seven years, the AEC modular misting booth is completely written off, while only 17.9% of conventional construction is written off.
- Using the above tax (35%) to determine a project’s true cost, the AEC Misting Booth returns 35% in tax savings to the company, where conventional returns only 6.3% (17.9% x 35%) in the first 7 years. If these tax savings, created by the accelerated depreciation, are invested over the next 31 years, the cost advantage of the AEC Misting Booth becomes even more pronounced
- Additional factors to consider:
- Responsible party.
- Elevated drain pan to remove requirement of recessing client’s floor.
- Detailed FAT, SAT with documentation.
- Regulatory certifications on control panel and plumbing assemblies.
- Warranty and Technical Support.
What is the difference between an AEC Misting Booth and a Fogging Booth?
Mist is a cloud-like aggregation of minute globules of water suspended in the air, reducing visibility to a lesser degree than fog. Fog is generally described in meteorological terms as a cloud that touches the ground. For an individual outdoors, fog occurs if visibility is less than 200 meters, otherwise it is known as mist. In comparison, the high concentration of water droplets suspended in air inside an AEC Booth would reduce visibility to less than 10 meters. However because the AEC booth creates this fog artificially though banks of impingement nozzles, we call this process Misting, rather than Fogging, and is why we use the term Misting Booth.
Immediately next to the AEC misting nozzles the water droplets do have a slight but detectable impact, but within a matter of inches from the nozzle, the droplets have virtually no residual momentum from the nozzle; their paths are determined by air currents and by gravity. The exact droplet size distribution is dependent upon the supply water pressure; however with water pressure of 60 psig, the majority of droplets are less than 50 microns (0.002in) in diameter, and small enough to remain airborne for at least 20 seconds after the spray is turned off. As a comparison, human hair is about 0.004in diameter that equals 100 microns. Breaking one gallon of water into 50 micron droplets will produce about 68 billion droplets of fog.
Where and when are AEC Misting Booths used?
- Wherever there is open handling of highly hazardous powders.
- When there is a possibility of an isolator breach.
- Whenever maintenance is required on high containment enclosures.
- Most commonly used in Pharmaceutical and Fine Chemical Industries.
- Used as an intermediary stage between processing area and degown area.
What is the difference between an AEC Misting Booth and a Decontamination Shower?
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MISTING BOOTH
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DECONTAMINATION BOOTH
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Can I use the AEC Misting Booth as a Decontamination Booth?
If the misting cycle is increased from 30 seconds to 2+ minutes, the mist generated by the AEC Booth will fully saturate all surfaces of the operator’s outer layer, coalescing with other water droplets and sheeting (streaming) water down to the drain basin, taking the dissolved contaminant with it.
From an EH&S perspective, using an AEC Misting Booth as a Decontamination Booth (wash off all contaminant on the suit) may at first appear to provide merit, for it accomplishes the goal of washing the suit without the disadvantages that traditional decontamination showers have, such as, reasolizing particles by the strong shock of forceful water jets. With the suit washed of contaminants, there would appear to be a much lower respiratory and cross contamination concern during degowning. However using a misting booth as a gentle decontamination booth is generally not recommended for the following reasons:
- Most companies have replaced washable outer layer protective suits with disposable ones. Washing a suit is time consuming and creates lots of waste water. Ensuring the suit’s cleanliness can be very difficult and impractical to test for. With most companies using disposable suits, there is no need to go through the effort and expense to wash the suit of contaminants.
- Disposable suits use a non-woven hydrophilic material, however they are not waterproof. If saturated with enough moisture, these suits will allow water to bleed through the material, allowing penetration though the seams, zipper, neck, cuffs and ankle region. Any dissolved powder on the suit may then seep through onto the operator’s skin and under garments, providing dermal and future contamination possibilities.
- The standard 30 second misting duration provides just enough light wetting of the suit as to cause powder to stick without causing run-off and bleed though concerns. This short time span only causes a small delay in operations, even with a multiple person shift. Expanding the cycle time to 2+ minutes will impact operational efficiency.
- Affixing the powder to the suit, placing a suit in a bag, and sealing the bag contains the spread of contamination. It’s easy to dispose of the suit through incineration, and the suit needs to be disposed of regardless if the suit was washed or just misted.
- Using a longer misting cycle to decontaminate a suit requires treating the waste water, which can be much more expensive and difficult than if the contaminant stayed affixed on the outer suit.
Can I integrate the AEC Misting Booth with a different company’s modular wall system?
The AEC Misting Booth can be just as easily integrated into a modular wall system as it can be integrated into a client’s drywall or cinderblock wall construction. All that is necessary is that a cutout in the client’s wall is provided to allow the AEC Misting Booth to mate up to. Any gaps created can be sealed with SS trim or caulking.
Why not use an Air Shower to clean the operator of powder before degowning?
Air Showers are used for an engineered Entry System into a high classification clean room environment. The Air shower helps to clean an individual of normal particulate, such as dander or dust and is not intended for operator protection. Air showers do nothing to fix or control the spread of contaminants. The air streams do help drive off particulate from the garment but the particulate just settles someplace else. Air showers are now generally replaced by misting booths for degowning operations when potent dusts are involved.
Why does AEC use water pressure only impingement nozzles and not Air Atomizing or Ultrasonic Nozzles?
- The atomizing nozzles are very noisy, especially when banks of nozzles are used, which may necessitate hearing protection. The AEC impingement nozzle design runs almost silently.
- It is very difficult to maintain air to water balance correctly to generate a good atomizing mist.
- Air atomizing nozzle mist is very aggressive near the nozzle and the airstream adds a turbulent mix that can dislodge particles instead of gently wetting them if the operator stands too close to the nozzle.
- Air atomizing nozzles create a very fine particle size, however due to the small confines of a misting booth the spray tends to be too aggressive and far too noisy for the desired application.
- Ultrasonic mist foggers typically require carrier air to deliver the mist because the forward momentum and particle size is too small to project the mist out and onto the operator. This carrier air can disturb the dust particles on the suit, creating a respiratory and contamination concern.
- Ultrasonic mist foggers are difficult to clean, expensive to replace, requires a high voltage power source.
- Ultrasonic mist foggers are very sensitive to the effects of scaling with hard supply water and should be used only with distilled water and a demineralization cartridge. If typical city water is used, the water hardness will, overtime, reduce the mist quality and create ‘white mineral dust’ which can settle inside and outside the booth, coat surfaces and cause respiratory irritation.
Can a solution other than water be used in the AEC Misting Booth?
Solutions other than water have not been considered by AEC for the Misting Booth. The heavy fog created by the nozzles is breathed in by the operator. If, for example, a sporicide or other acidic additive was added to the water for vaccine or biotechnology applications, extreme caution would be needed to protect the operator’s face, eyes, and breathing from the solution.
What to do with the waste water?
AEC Misting Booths utilize very little water, approximately 1 liter per misting cycle, with the average misting cycle being 30 seconds. Because the mist causes powder to stick to the suit vs. washing it off (assumes the operator does not over saturate himself by exceeding the recommended mist cycle duration time), most of the contamination will stay with the suit after degowning, in which the suit is placed and sealed inside a plastic bag. However there will be a very small amount of contamination from dust that managed to become airborne and encapsulated in the mist, as well as small amounts of dissolved product from runoff generated by the slippery suit as some mist droplets collect together and run down to the floor grate.
Due to the very small amount of waste water produced and the fact that most of the contaminant remains on the protective clothing and is not washed off, waste water is most frequently drained to a sanitary sewer. Alternately, waste water can be drained or pumped to a holding tank, where it can be sampled and released to sanitary sewers or pumped to a processing area if it needs to be treated. If waste water needs treated or tested before draining and the client is unable to pump or drain to a holding tank, the client can plug the misting booth drain basin (holds 9 gallons of water). Waste water can then be tested.
Most of the waste water generated by the booth will occur during cleaning operations, not by the misting cycle itself. The booth walls and drain basin can be wiped down for thorough cleansing, and the misting booth interior needs to be washed down with a hand held sprayer or with the optional Wash in Place rotating nozzle located in the ceiling. The frequency of cleaning is determined by the client, however it is recommended to wash the interior of the booth at least once after every shift to flush out all potentially harmful encapsulated dust before it dries and becomes a respiratory concern.
Waste water created by the cleaning operations can range from 2 gallons (if using a hand sprayer) to 10 gallons if using the Wash in Place system. The waste water must be removed, which is why using an absorbent pad to collect the water is not recommended. Instead, gravity or pump-out draining needs to be implemented.
What type of performance testing was conducted on the AEC Misting Booth?
Protocols were developed during the AEC Misting Booth design phase to test efficacy of the mist delivery system, nozzle placement, and water pressure. Booth dimensions needed to allow for operators of all sizes to comfortably maneuver inside, yet small enough to ensure there were no dry regions where the cone shaped misting pattern could not spread to.
Once the booth shell dimensions were established, placement of the nozzles necessitated dye testing of an operator’s PPE with differing misting time intervals, ensuring there was uniform mist coverage and no region was over saturated or under saturated. Dye testing allowed for enhanced visibility of the wetted regions on the white colored suit.
After the nozzle locations, type, and cycle times were optimized (based on the results of the Dye tests), a Surrogate Study was performed to test the effectiveness of the AEC Misting Booth at reducing airborne dust during the degowning operation inside a simulated degowning room.
Please see the overview of the Dye testing (used to determine mist coverage and cycle duration) and the surrogate study (used to determine the effectiveness of the AEC Misting Booth at reducing the airborne dust).
Dye Test
- An air sample is taken inside the misting booth using a vacuum wand to establish a background condition.
- Operator suits up in their PPE.
- Operator is lightly and uniformly dusted from head to toe with a dye that changes color when wetted.
- The operator stands inside the misting booth (without activating the misting cycle) and an air sample is taken around the operator.
- The operator turns the misting booth on.
- During this misting cycle, the operator twists his/her body and moves his/her arms up and down to reduce any folds in the PPE and to help ensure uniform coverage. After an adjustable duration (typically 15-40 seconds), the misting cycle automatically shuts off.
- Another air sample is taken (before the operator exits the booth), to demonstrate absence of airborne dye.
- The operator exits the booth and a visual inspection with a magnifying glass determines if there are areas on the PPE that have not changed color from the dye. If there are non-dyed areas, the inspector will mist that region with a spray bottle to determine if it changes color. If it does change color, it would be determined that that region was not properly wetted during the misting cycle. Corrective measures may then consist of increasing the misting cycle duration, altering the operator movement in the booth, etc.
Surrogate Study
Click here for a copy of the test report.
During the surrogate study, the AEC Misting Booth achieved an effectiveness factor of at least two orders of magnitude. The average airborne contaminant concentrations measured during the use of the misting booth were more than 200 times lower than the contaminant concentrations measured without the use of the misting booth.
