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Posts tagged with “UVGI”

Vartest has a FAQ on UVC/UVGI and Textiles

Vartest Is Performing Accelerated UVC Testing Of Contract Textiles

  • Anticipates years of healthcare end use exposure in weeks.
  • Permits ranking and product development of woven, knitted, nonwoven, and coated fabrics.
  • Multiple evaluation methods are available:
    • Visual assessment of shade change.
    • Spectrophotometric assessment of shade change.
    • Embrittlement
    • Topcoat degradation including changes in gloss and surface chemistry and physical structure.
    • Change in anti microbial activity.

Why is UVC important to Contract Upholstery?

Standards for UVC resistant materials have up until now mostly been the concern of space agencies, as the atmosphere absorbs all UVC radiation before it reaches the Earth’s surface.

Testing for resistance to lower energy UVA and UVB is included in textile standards for outdoor applications (e.g., AATCC 16 option 3), or for materials used long term in bright areas (e.g., curtains). Such materials are selected or designed for some level of UV resistance to naturally occurring UVA and UVB wavelengths.

UVGI exposes interior surface materials (such as contract textiles) which are not currently engineered for any UV resistance to even higher energy radiation than what is addressed by lightfastness and weathering tests.

The filtered xenon and fluorescent sources specified in AATCC, ASTM, and ISO are designed to reproduce naturally occurring solar radiation at the earth’s surface, so their spectra include no UVC. They cannot be used to determine how materials will behave when exposed to UVC.


Can UVA and UVB exposures be used to predict UVC results?

No.

Materials which deteriorate when exposed to UVA and UVB will also deteriorate when exposed to UVC.

However:

Materials which deteriorate when exposed to UVC will not necessarily deteriorate when exposed to UVA or UVB.

Increasing the exposure time or intensity will increase the number of photons delivered.

But it is the energy per photon which matters.

If the energy of a UVB photon is less than the dissociation energy (breaking strength) of an atomic bond, then no bonds will break no matter how many photons are delivered.

UVA and UVB are less likely to damage textile coatings, finishings colorants, and fibers.

UVC is more likely to damage textile coatings, finishes, colorants and fibers, as well as viral and bacterial DNA.


Dose

C. difficile is considered a benchmark for effective disinfection.

It is among the most difficult HAIs to disinfect by conventional methods, and this remains true for UVGI.

Exposure dose at 254nm to kill C. difficile is in the order of 0.8 kJ/m2.

Seven years is commonly considered the lifespan for furniture in a healthcare setting.

Exposure to this dose once a week, for 7 years gives a total germicidal dose of 291 kJ/m2. That is total exposure of 291 kJ/m2 using a germicidal lamp operating at 254 nm output. Vartest achieves this dose in 10 hours but recommends a longer exposure time.

Inverse-Square Law of Light

The exposure indicated is a minimum, as the furthest corners of the room must receive this dose in order to kill C. difficile. Typical healthcare scenarios involve more frequent and more intense exposure.

The inverse square law describes how dose falls off exponentially from the source. In order for a surface three meters away from the source to receive the recommended dose, a surface one meter away will be exposed to nine times that amount. Surfaces will also be exposed repeatedly as the source is repositioned.


Ozone Generating LPM Lamps and Air Purifiers

The spectrum of low pressure mercury lamps has a peak around 183 nm, which generates ozone.

Ozone is a powerful oxidizing agent, with deodorizing and disinfecting properties similar to hydrogen peroxide.

The glass envelope of the lamp is doped to block this wavelength for applications where this would be a health hazard.

Like UVC, ozone attacks polymers and soft plastics, fades dyes, and causes yellowing. AATCC 109 and 129 can be used to assess a textile’s propensity to degrade when exposed to ozone in either high or low humidity conditions.

This type of damage is colloquially known at “dry rot.”

Healthcare end users plan based on projected lifespans.

Coated upholstery materials designed to be wiped down are of special concern. An upholstered item damaged in this way becomes impossible to sanitize and should be repaired or replaced. Plastics are especially susceptible to UV embrittlement and discoloration, and even slight damage may render a coating permeable.

Contract materials for healthcare applications are engineered for heavy wear, but UVC exposure is likely to shorten the lifespan of materials only designed to resist chemical and mechanical degradation.

Materials and equipment which cannot be sterilized are unsuitable for use in a healthcare environment. Equipment designed to be easily cleaned may become unreasonably labor intensive or impossible to clean when damaged.

Cosmetic discoloration is considered a serious issue even if equipment remains functional.

For more information contact: Trevor Trapp ttrapp@vartest.com Phone: 212-947-8381 Cell: 917-887-3202