A pass through cabinet is an enclosure installed in a wall between two or more adjacent spaces to facilitate the transfer of materials from one side to the other. Pass through cabinets play a vital role in cleanrooms and other controlled environments. They reduce foot traffic, improve cleanliness, safety, productivity, and much more (read more on the benefits of cleanroom pass throughs). Instead of garbing up to carry materials into a cleanroom, personnel can simply place materials in the pass through transfer hatch for fast, convenient transfer into the cleanroom.
Terra offers many pass through cabinet designs with application specific features to help maximize cleanliness and safety, plus lower operating costs.
A defining feature of a cleanroom pass thru is a door interlock mechanism (mechanical or electronic) that allows only one door to open at a time. This creates an air lock for safer transfer by minimizing cross contamination that can occur between rooms when both doors are left open at the same time. Keeping one door closed also helps maintain differential pressure in the room. A large enough hole in the cleanroom can cause a significant drop in differential pressure that could compromise the cleanroom’s cleanliness classification.
Interlock systems can be manual or automatic. A manual interlock system can cause problems because it adds an extra step that is prone to human error. For example, operators need to remember to lock the door after the door is closed. Accidentally forgetting this step can cause frustrating and costly operation delays.
All of Terra’s door interlock systems are automatic, eliminating any possibility of forgetting to lock a door. When one door is opened, the opposite door automatically locks to prevent both doors from being simultaneously opened. Terra offers different door interlock options to match your application’s cleanliness and operating needs. They are rated for millions of operations, ensuring long-lasting and reliable service.
Terra’s ValuLine™ cleanroom pass thru windows and general-use pass through cabinets use retaining brackets to hold the chamber to the wall. The bracket on the clean side is welded to the chamber. The one on the opposing side slides onto the chamber and fastens to the wood or metal framing that surrounds the wall cut-out. The screws mounting these chambers penetrate the cleanroom wall.
Terra’s CleanMount® pass through cabinets use a unique clamping system that requires no hardware or fasteners to penetrate the cleanroom walls and mounts in just a few minutes. As long as the wall cut-out is finished and sealed, you can quickly install or remove the pass thru cabinet without a costly cleanroom shutdown and re-validation.
To perform maintenance without contaminating a classified space, you first seal off the “dirty side” with plastic sheeting to maintain the positive-pressure differential. Loosening two lag bolts lets you lift the pass through out of the wall without contaminating the room. Once out, the pass through can be serviced, modified, or even replaced with an upgraded version to accommodate new applications.
Terra offers both flush mount and center mount cleanroom pass box designs. The CleanMount® system mounts flush against the cleanroom wall to minimize particle accumulation and simplify cleaning. Flush-mount chambers protrude into the “dirty” side room and can be braced with support brackets if needed. Alternatively, chambers can be specified for center-mounting in nearly any wall thickness. Electronic pass through cabinets can even be specified with access doors on adjacent corner walls with a 90 degree pass thru cabinet design. These designs can also be specified mounted to the floor as a cleanroom cart pass through to efficiently roll through materials or large equipment.
Weld construction is an important consideration for sterile applications. Tack welded or stitch welded stainless steel pass thrus are easier to build and lower cost, however the non-continuous intermittent welds leave hard-to-clean cracks and crevices that can harbor germs and other contaminants. This makes chambers with partially welded interiors unsuitable for sterile operations and other applications with strict cleaning protocols.
A fully-welded stainless steel pass through box has continuous seam welds and smooth, formed radius corners. This improves cleanliness and simplifies wipedowns by removing any cracks or crevices for particles and microbes to collect.
All CleanMount® pass throughs feature continuous seam welds with smooth, coved corners for a seamless interior that is easy to clean and sterilize. Doors feature a lift-off design for easy removal and cleaning, and 304 or 316L stainless steel surfaces stand up to common cleaning agents, including IPA. Terra’s ergonomic LiftLatches operate without metal-on-metal scraping inside the chamber, a common source of contaminants with rotary-style latches.
For the most demanding sanitary applications, specify Terra’s BioSafe® pass through, which includes an autoclavable doors with blue elastomeric door seals. BioSafe® pass throughs also feature a fully welded body with coved radius corners and knife-edge hatch openings. All chambers can be electropolished upon request.
Read more on the benefits of BioSafe® pass through chambers.
Specify replacement doors, for the same reason you carry a spare tire in your car for a flat tire. Terra's pass through chambers can last indefinitely with proper maintenance. Unfortunately the doors are sometimes damaged by users unintentionally mishandling and applying excessive force. This is even more common in high traffic areas such as hospitals. Ordering a replacement door after the pass through chamber is out of service can cause costly disruptions to your cleanroom or lab operations. To avoid these problems, proactively order replacement doors at the time you purchase the pass through chamber; simply add "-RH" (for right-side hinge) or "-LH" (for left-side hinge) to the part number of the chamber.
Terra offers several cleanroom pass through accessories to increase productivity and automate processes that would otherwise be done manually:
Fire-rated pass through cabinets help protect your personnel, equipment, and facility by maintaining the integrity of your facility’s certified fire-rated wall. Terra offers several fire-rated pass thru chamber configurations with doors that bear the UL-10B label for 90-minute fire exposure, suitable for a 2-hour fire wall rating. Models are available with and without viewing windows, on all designs (ValuLine™, CleanSeam™, CleanMount®, BioSafe®, Smart®), and in chamber sizes up to 33”W x 36”D x 45”H. The default design includes a fire-rated door on one side of the chamber, and a standard non-fire-rated door on the opposite side. They can be customized to include fire-rated doors on both sides of the chamber.
304 stainless steel is one of the most common types of stainless steel used in the clean room industry although it can be problematic for some applications that use corrosive chemical cleaners like bleach. Chlorides can degrade stainless steel, causing pitting corrosion. Pitting sheds contaminating particles and creates crevices where microbes can accumulate.
316 stainless steel contains more nickel and molybdenum than 304, which enhances its resistance to pitting corrosion in wet environments, and also from harsh chemicals used in cleaning agents. 316 stainless steel is also more resistant than 304 stainless steel for high-temperature sanitation processes. For this reason, 316 stainless steel is ideal for any application with exposure to harsh chemical cleaners or severely corrosive environments which 304 stainless steel cannot withstand. Terra Universal offers pass thru box designs with 316L stainless steel, a low-carbon variant of the standard 316 alloy, for even higher resistance to corrosives.
Read more on the benefits of 316 stainless steel.
For biological applications, a UV-C sterilization lamp with safety circuit kills or neutralizes microbes, including viruses and mold spores, before sample transfer into a sterile lab.
Pass through chambers can also be configured as air locks to reduce the likelihood of cross contamination by lowering particle counts inside the passthrough. A pass thru air lock can be ventilated using positive pressure, negative pressure, or recirculation.
A pass thru cabinet with passive ventilation has no additional air supply and relies on the pressure cascade from the cleanside to provide air flow through the enclosure. Terra can install ULPA filters on one or both sides for filtered leakage paths to inhibit the passage of contaminants.Active ventilation
A pass thru cabinet with active ventilation (or dynamic pass through box) has a dedicated air supply connected to the chamber for added protection. They fall into three categories: supplied (positive pressure), exhausted (negative pressure), and internally recirculated (negligible pressure change). Note that both positive and negative pressure configurations can affect adjacent room pressure balances and should therefore be accounted for accordingly in cleanroom airflow designs.
A cleanroom pass through box with supplied ventilation provides a single pass (open loop) supply of filtered air. This creates a clean positive pressure environment and prevents particles from entering the chamber. These pass through chambers can be configured to include an exhaust filter or duct collar to send excess air to the building air-handling system or adjacent unclassified room.
HEPA filtered air shower pass throughs can be configured for positive pressure. These units use high velocity jets of HEPA filtered air to help decontaminate equipment prior to entering or exiting a cleanroom. The supply fan turns on when one door is opened and stays on for a user specified duration after the door is closed.Exhausted ventilation (negative pressure, open loop)
A cleanroom pass through chamber with exhausted ventilation (also known as a sink airlock) provides a single pass (open loop) supply of exhausted air. This extraction system creates negative pressure to prevent particles from escaping the chamber from either door. This design can be used for applications where hazardous materials or particulates must be contained and kept from passing through either side of the chamber. Ventilation units can also be used to duct fumes that might be present in a specimen, allowing the pass through to act as a drying system. Specify a flange adapter to allow connection from the pass through chamber to an in-house ventilation system. Exhaust air speed sensors can also be configured for added safety to alarm in the event air speed falls below a specified setpoint.Internally recirculated filtration (closed loop)
Recirculated pass thrus use a closed loop system to continuously recirculate air in the chamber through built-in HEPA or ULPA filters. These clean air pass thrus are self-contained and do not require any ventilation or exhaust ducting. They run continuously to reduce particle concentration within the chamber. This design is commonly used because the closed-loop system does not impact adjacent room pressure balances when operating.
With heavily mandated cleanliness requirements associated with USP 797 and USP 800 cleanrooms, a pharmacy pass thru is a vital point for sterile pharmaceutical compounding. Terra’s HEPA filtered pass through and Smart HEPA filtered pass thru use recirculating ventilation to meet and exceed USP 797 and USP 800 guidelines.
Terra offers many innovative solutions to protect specimen inside a cleanroom transfer hatch from theft or unauthorized access: