Autoclave Wall Seal Options, Explained

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Written by: Scott Mechler

BS Mechanical Engineering, Mechanical Engineer

Though less flashy than other parts, the wall seal around a pass-thru (double door) sterilizer s one of the most essential components of apass-thru autoclave’s design. That’s because this seal creates a barrier between the contained room and non-contained room (or clean room vs dirty room) thereby preventing any possible contaminants from escaping the room.

In this article, we’ll take a closer look at the two most common types of autoclave wall seals — air differential seals and bioseals — including how they work, which applications they’re best suited for and how they’re installed.

Air Differential Seal vs. Bioseal: What’s the Difference?

An air differential seal refers to any seal that prevents the bulk passage of air between areas maintained at a pressure differential. In most autoclave builds that use an air differential seal, a stainless steel barrier flange is welded to the periphery of the sterilizer. A closed-cell silicone gasket secures the welded seal to the wall, permitting normal expansion and contraction of the building.

A bioseal — short for biological sealing flange — employs a stainless steel barrier flange welded to the periphery of the sterilizer while another stainless steel barrier is attached to the wall opening through which the autoclave is installed. Bioseals prevent the passage or airborne microorganisms from the contained side of a sterilizer to the uncontained side. A single piece closed-cell silicone gasket completes the seal between the building and the sterilizer, thereby ensuring that seal integrity is not compromised during normal expansion and contraction of the building.

For more details on the differences between air differential seals and bioseals, please refer to the chart below. Note that one of the key differences between an air differential seal and a bioseal is that only the latter creates an airtight seal.

Type Air Differential Seal Bioseal
Construction Stainless steel barrier flange is welded to the periphery of the sterilizer and solid-silicone gasket. Stainless steel barrier flange is welded to the periphery of the sterilizer and solid-silicone gasket.
Mounting Does not use wall plates; can be through-bolted.  Suitable for modular walls. Uses wall plates to ensure airtight seal.
Wall Type Can use modular wall; does not require stud or rigid wall construction. Requires stud or rigid wall construction, such as concrete, in order to mount wall plates.
Smoke Test Some smoke will get through; not airtight, but better than standard installation. No smoke will get through; airtight seal.

When Should You Use an Air Differential Seal vs. a Bioseal?

Whether you use an autoclave with an air differential seal or a bioseal depends entirely on the Biosafety Level of the facility.

Established by the Centers for Disease Control and Prevention, biosafety levels are a series of biocontainment protocols designed to protect laboratory personnel, as well as the surrounding environment and community, from potentially hazardous materials.

There are four biosafety levels; the lowest, Biosafety Level 1 (BSL-1 applies to any facility that specializes in the research of nonlethal agents that pose a minimal threat. The highest, Biosafety Level 4 (BSL-4), applies to specialized research laboratories that handle potentially deadly infectious agents — for example, the Ebola virus.

Intro to Biosafety Levels: Basic Requirements & More >>

Air differential seals are acceptable in most BSL-1 and BSL-2 laboratories; if the laboratory is rated BSL-3 or higher, you’ll need a bioseal. Given that BSL-4 laboratories are exceedingly rare and have complex requirements, for the purpose of this article, we’ll focus on BSL-3 facilities.

One of the key criteria for a BSL-3 facility is that all bacteria and pathogens must be contained within the lab; the lab itself must be physically separate from access corridors and feature self-closing, double-door access. In that same respect, any autoclave in a BSL-3 laboratory must have two doors in order to allow goods to pass through the autoclave from the contained room to the non-contained room. Each of these doors must be equipped with a bioseal in order to provide separation and create a positive seal between the contained and non-contained sides, thereby preventing any possible microbial contamination.

How Are Air Differential Seals and Bioseals Installed?

Installation for an autoclave with an air differential seal differs from that of an autoclave with a bioseal.

Air differential seal autoclaves install a bit more easily than bioseal autoclaves, as they do not require the heavy metal wall plates that must be anchored around the wall opening prior to installation. Instead, the rubber gasket is installed directly around the wall opening and secured using clamping bars. Air differential seal units can also accommodate a modular wall construction, which is not possible with bioseal units.

As mentioned above, bioseal autoclaves are equipped with a biological cross-contamination barrier flange seal. This flange seals the wall opening around the autoclave to prevent the escape of biological agents from a BSL-3 lab. The flange is constructed from stainless steel and is fully welded around the perimeter of the autoclave to create an airtight connection. The flange also mates up to a silicone gasket using stiffening bars, which are held in place by stainless steel nuts, bolts and lock washers.

Any organization interested in purchasing a bioseal autoclave can choose between cabinet installation or recessed installation; both options are illustrated in the GIF below.
Installation Animation
Need help figuring out which autoclave seal you require for your laboratory or research facility? With 75 years of experience manufacturing and installing steam sterilizers for the world’s leading hospitals, universities and biotechnology facilities, Consolidated Sterilizer Systems has the necessary expertise to help you identify the right option based on your sterilization needs. From single door and dual chamber units to our bioseal equipped, BSL-3 approved pass-thru autoclave, we offer the right autoclave for any environment.

Find out what Consolidated can do for you — contact us today to get started.

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