Cleanroom Decontamination - Farewell to Formaldehyde!

Formaldehyde has been used in an increasing number and range of common applications since the first successful isolation of the pure chemical in 1892 by the German chemist, Friedrich August Kekule' von Stradonitz.

Today, Formaldehyde is the public sector’s first choice of disinfectant for cleanrooms. Its popularity is mainly due to its efficacy for killing the toughest bio-contaminants plus the low cost of the chemical and its complementary decontamination equipment.

Yet recent EU legislation has reclassified formaldehyde as a Class 1B carcinogen and Class 2 mutagen, placing the widespread use of this popular chemical under threat. What will this mean for cleanroom decontamination and what are the realistic alternatives?

Formaldehyde is more than a European issue

While the Biocidal Products Committee (BPC) have not yet announced their decision on rejecting or accepting formaldehyde as a biocide in the PT2 category, the expectation is that it will indeed be rejected. If rejected, formaldehyde fumigation within laboratories will become illegal across the EU. Should the decision be announced before Brexit is affected, the altered regulation will be written into UK law.

Whatever the future holds for the UK’s relationship with the EU, the UK Health and Safety Executive (HSE) has voiced its doubts at the future use of formaldehyde as a biocide. In the July 2015 edition of its “Biological Agents eBulletin”, the HSE presented the following statement (published in bold text):

“(the) HSE therefore recommends that users start to look into the development of alternative gaseous disinfectants for rooms and equipment, whilst there is time to do so.”

Disadvantages of Formaldehyde for Cleanroom Decontamination

The short-term headache of replacing formaldehyde in the decontamination process could bring many long-term benefits.

Microbiology Product Specialist and former cleanroom operator, Andrew Ramage, explained two obvious benefits to the UK public sector’s preference for formaldehyde as bio-decontaminant:

  • “Formaldehyde is very cheap and delivery requires no more than the use of a common metal kettle.”
  • “Formaldehyde is highly efficacious in scenarios of organic soiling – even Mycobacterium tuberculosis is no match for formaldehyde.”

Despite these benefits, Ramage believes that the cons of using formaldehyde outweigh the pros:

  • Apart from the chemical’s now confirmed carcinogenic nature, it requires long contact times (6-12 hours) to effectively decontaminate an area.
  • The chemical is also highly sensitive to humidity, which adds the burden of humidity control to the decontamination process.
  • Decontamination with formaldehyde leaves behind a residue that must be physically cleaned away. This is especially difficult in hard to reach spaces, such as the inside of HEPA filters.

Formaldehyde Alternatives for Cleanroom Decontamination

Ramage is in no doubt that it would be a good call for facility managers to start looking at formaldehyde alternatives. Top substitutes to be considered include chlorine dioxide, vaporised hydrogen peroxide (VHP), peracetic acid formulations (e.g. Minncare Cold Sterilant) and Ozone decontamination.

While chlorine dioxide is indeed a very efficacious bio-decontaminant, Ramage warns that its delivery system is expensive and that the installation may require significant modification of the laboratory.

Another alternative to be investigated is Vaporised Hydrogen Peroxide (VHP). While this chemical requires a long contact time, it is very efficient in eradicating a range of bio-contaminants that are common to pharmaceutical cleanrooms. However, VHP has not been proven adequate for destroying bio-contaminants that are commonly found in public sector high bio-containment level laboratories, most notably, Mycobacterium tuberculosis. While tests have shown it to be effective for stunting the TB bacterium, it does not terminate the cells entirely. VHP can, therefore, be considered an ideal alternative for the pharmaceutical sector, but not for TB-containable facilities as is common in the public sector.

Peracetic acid formulations distributed by dry fog systems is another viable replacement for formaldehyde as bio-decontaminant. In A Roadmap for Investigation and Validation of Dry Fogging as a Decontamination Technology, Samantha Kimball from Calian Technologies LTD describes the benefits of this solution:

“Dry Fogging Systems (DFS) can employ solutions containing peracetic acid which is effective against a broad spectrum of microbes, non-corrosive, non-toxic and environmentally safe and hence has particular applicability when the organism to be decontaminated is unknown or needs to be applied in the field.”

Ramage is in agreement with Kimball’s positive review of this solution:

“Peracetic acid doesn’t leave any residue and distribution is effective in a short period of time. The entire process of dry fogging with peracetic acid, from start to finish, takes as little as two to five hours.”

Switching over from Formaldehyde? Beware!

The alternatives mentioned above should provide the facility manager with a good starting point for selecting a formaldehyde alternative. Making the switch, however, should be undertaken with care. Ramage calls on facility managers and operators to heed the following three factors: chemical residues, penetration ability, validation.

  1. Residue

Cleanrooms must undertake extreme care in eliminating formaldehyde residue before using a different disinfectant. Formaldehyde is known for leaving a residue on surfaces; from the surface of countertops to inside HEPA filters. Any residual coating of formaldehyde could react with the new chemical, resulting in corrosion or the creation of toxic fumes.

  1. Penetration

Before selecting a disinfectant, managers must consider their decontamination requirements in terms of spillage. A chemical that has been proven effective for killing the bio-contaminants in question might not be effective in scenarios of organic spillage due to a lack of penetration ability, for instance.

  1. Validation

Any facility’s decontamination needs depend on the nature of the bio-contaminants and the scope of spills it is exposed to. For this reason, it remains the responsibility of the operator to validate the efficacy of any disinfectant and/or decontamination technique that is used.

Farewell to Formaldehyde: “It’s not us, it’s you!”

While several European countries have already ceased using formaldehyde, some have made the mistake of stockpiling large quantities of this chemical. Therefore, the potential removal of formaldehyde from the PT2 category is likely to cause a variety of responses.

From a cleanroom operator’s perspective, Ramage calls it good riddance. “It’s horrible stuff, and working in its proximity has an immediate and long-lasting impact on your health,” he says. “I’m willing to bet that no cleanroom operator will miss it once it’s gone.”

Download Cherwell's Guide to Cleanroom Decontamination

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