Choose cleanroom insulation to avoid fungal contamination

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Fungal contamination, most commonly by molds and yeasts, is bad news for cleanroom manufacturing of pharmaceuticals. An outbreak can lead to everything from product recalls, with damage to brand reputation, and production shutdowns, to actual damage to the health of patients.

From a production point of view, the relatively common fungus Aspergillus Niger is known to contaminate raw materials stored in cold rooms before manufacturing in a clean room. As for the impact on the health of patients, contamination can reduce the therapeutic effectiveness of drugs. Creams and ointments are a prime example of products whose effectiveness can be compromised because many fungi live off keratin, a protein found in the skin, nails, and hair.

The fungal meningitis outbreak in the United States in 2012 that killed more than 100 patients and affected 798 others after receiving injections of contaminated steroids manufactured by the New England Compounding Center (NECC) in Massachusetts. As of December 2012, 400 lawsuits had been brought against the company as it filed for bankruptcy. Federal prosecutors have charged 14 former NECC employees, including its chairman, with a host of criminal offenses, including sending unsanitary or contaminated drugs.

Easy starter for mushrooms

Contamination control is made more difficult by the physical characteristics of fungal spores, which vary from 1 to 50 µ, and the ease with which they can enter environments by a wide variety of routes. Airborne spores can enter through windows or through ducts and drains – openings that also allow moisture to enter, in liquid or vapor form. This increases the relative humidity (RH) of the air, and high RH is a major contributor to contamination.

There are other routes of entry for contamination. As already stated, raw materials can be contaminated before entering the cleanroom, and the human factor should not be overlooked, as employees can also bring the contamination into the cleanroom. There is more than one example of athlete’s foot causing an outbreak.

Once established in the cleanroom environment, fungal spores spread relatively easily and aggressively, and eradicating them can be difficult. There are tons of tips on how to get rid of mold, but prevention is infinitely better than cure. In practice, this involves specifying materials and components that will resist the growth of molds, fungi and other microbial species, while providing the chemical stability, durability, purity and fire resistance that are essential characteristics. materials used in the construction of clean rooms.

Extremely important

The right choice of insulation is particularly important. Condensation is a common cause of contamination, with cold pipes being a major concern wherever the temperature of the pipe surface falls below the dew point of its surroundings. As the air cools, the water vapor concentrated in the air begins to condense and, at the dew point for a given temperature, it saturates in the air and condenses on surfaces. in the form of droplets, an ideal breeding ground for mushrooms.

A variety of cleanroom insulation products are available, under different brands and made from different materials. The main solutions commonly found in clean rooms are:

  • open cell melamine foam
  • EPDM elastomers
  • Closed cell PVDF polymer foam.

So how do cleanroom designers go about choosing the best insulation? Of course, the product chosen must meet recognized performance standards, which in this case are set forth in ASTM G21-15 (2025) Standard Practice for Determining Resistance of Synthetic Polymer Materials to Fungi. This involves inoculating samples of the material to be tested with appropriate organisms and then exposing them to conditions favorable for fungal growth. At regular intervals, samples are examined and evaluated for visual signs of growth.

Valuable because ASTM G21-15 certification is in the selection process, however, it does not reveal the performance of the respective solutions against each other under the same test conditions. Such comparisons are particularly important when the project’s budget limitations may prompt decisions to be made solely on price. Where possible, investment choices should be based on the most comprehensive knowledge, taking into account factors such as the impact of catastrophic failure due to contamination and ongoing service and maintenance costs. Increasingly, durability is another key consideration.

It is possible to find test results for individual brands in the public domain, for example, a manufacturer of open cell melamine insulation has published test results showing that fungal growth is evident after 21 days on its product. Open-cell melamine-based – but genuine as-the-like comparisons have proven elusive so far.

“Put the best to the test”

This is why, for the first time in the cleanroom insulation industry, Zotefoams, the foam specialists behind T-FIT technical insulation, commissioned independent performance tests that pitted T-FIT Clean against the leading brand of EPDM elastomeric foam insulation to provide a suite of verified results.

T-FIT’s story began over ten years ago, with customers in the pharmaceutical and biotechnology industries looking for a high performance insulation solution for cleanroom piping. T-FIT Clean, the first product line produced from ZOTEK F42 HTLS high performance PVDF foam from Zotefoams, quickly gained recognition and countless installations in these industries and in semiconductor cleanrooms attest to the performance and the longevity of T-FIT Clean.

Murphy & Son, based in Nottingham, UK, was appointed to perform the testing based on over 130 years of experience supporting the brewing industry, where the fermentation process presents a risk area recognized fungal contamination and its consequences are well understood.

During testing, samples of T-FIT Clean and EPDM were pre-cleaned with 70/30 ethanol

water to remove any surface contamination that may promote mold growth. In temperatures of 28-30 ° C and relative humidity ≥ 85%, they were then exposed for 28 days to a variety of fungi (Table I), including the two most commonly found in a clean room environment. – Aspergillus and Aureobasidium.

Upon completion of testing, samples were inspected closely for signs of mold growth with the naked eye and up to 50X magnification. The degree of growth was then evaluated and expressed as a function of the

scale provided for in point 9.3 of the ASTM G21-15 method (table II).

The verdict

The T-FIT Clean sample tested received a mold growth index of 0, with no signs of growth observed, as shown in these post-test photos and close-up images of the sample (Figure 1).

In contrast, the EPDM elastomeric foam product was rated 2 and, as shown in the images below, exhibited clear visual evidence of mold growth (Figures 2 and 3).

Clearly superior

Thanks to these tests, the market now has concrete evidence of T-FIT’s industry-leading resistance to fungal contamination, clearly demonstrated by the score 0 against the score 2 of the market-leading EPDM elastomeric foam. This exceptional performance is the result of the characteristic high purity of the “inert” surface of T-FIT products, which does not readily promote the growth of microorganisms.

Key to the performance characteristics of T-FIT products is Zotefoams’ unique three-step manufacturing process, which uses pure nitrogen as a foaming agent to create materials of exceptional caliber compared to foamed products using chemical foaming agents. In step 1, the pure PVDF polymer is extruded into a solid plate, then irradiated to create chemical bonds that join the polymer chains (crosslinking). The resulting material properties include excellent thermal stability, high strength and toughness compared to uncrosslinked materials; irradiation crosslinking also avoids the shrinkage often associated with thermoplastic materials. Step 2 applies extremely high pressures and temperatures to dissolve the nitrogen gas in the slabs. In step 3, the nitrogen saturated slabs are subjected to a second high temperature, low pressure cycle where the pressure is gradually released to allow free expansion of the foam sheet material.

The result is a fine, completely enclosed cell structure that is free from fibers, dust and particles, and very resistant to the growth of bacteria and mold. T-FIT Clean’s ASTM G21 tested performance on zero fungal growth provides long-term protection against the risk of product contamination. Compared to open cell materials, T-FIT more effectively limits the penetration of moisture and gas because there is no continuous network through which substances can travel.

For high temperature environments, T-FIT Clean offers exemplary references in fire safety. Rated 5/45 (Flame Spread Index / Smoke Development Index) according to ASTM E84 for surface burning characteristics of materials, T-FIT Clean offers Flame, Smoke and Toxicity Index the lowest of all polyester / elastomer insulation.

A wide operating temperature range – from -80 ° C to +160 ° C – combined with the durability of the material ensures that thermal performance remains intact over the long term, even with repeated cycles between refrigerated process temperatures and High cleaning temperatures (clean-in-place, sterilize-in-place) is involved.


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