Personal Protective Equipment (PPE)

HAZMAT SUITS (COVERALL)

Use of right material & following right process are most important for processing any Personal Protective Equipment (PPE).

 

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PPE Selection and Compliance

Use of right material & following right process are most important for processing any Personal Protective Equipment (PPE).

Considering the common routes of contamination from COVID-19, the PPE for front line medical workers should have blood & viral penetration resistance equivalent to AAMI Level 4.

  • As the common method of joining fabrics is sewing, which creates needle penetration holes along seam, it is paramount that both fabric and seam are compliant to ISO 16603 / ASTM F1670 (resistant to synthetic blood and body fluid penetration) & ISO 16604 /ASTM F1671 (resistance to viral penetration) standards.
  • Of these, the ISO 16604 test is commonly considered the most important because it uses a synthetic blood infected with a “bacteriophage” to assess penetration.
  • Critically for this analysis, the bacteriophage used is a much smaller size (0.027 microns) in comparison to Coronavirus 2019-nCoV (0.125 microns) .Thus passing the ISO 16604 test at a high class is a good indicator that a fabric and seam are unlikely to allow the virus to penetrate, regardless of the medium.

PPE Processing & Methods

The PPE are of two types ie., gowns and coveralls. In this document, we will explain processing of medical coveralls (also commonly called Hazmat suits), which is basically hooded top joined with trouser at waistband.

There are two ways of making coverall AAMI 4 level compliant.

First of all choose fabric (Spun Bond Polypropolyene – PPSB) which are already compliant to above two tests.

The fabric can be joined by either Classical method (traditional stitching and then seams are sealed by tapes) (or) Modern method (Ultrasonic welding).

While stitching can be done by either single needle lockstitch or 4/5 thread overlock, seam sealing can be done by hot air seam sealing machine.

The hot air seam sealing machine uses adhesive tape as consumable. The machine produces hot air with precisely controlled temperature to directly heat up the adhesive of seam tape.

The heated tape and the fabric are feeding into two oppositely rotating rollers under pressure called nip rollers.

Types of Seam Sealing Tapes

For a medical PPE a 2 layer seam sealing tape can be appropriate, which are designed to seal seams on light to medium weight Vinyl or Spun bond PolyEthylene coated fabrics (PPSB) .

  • According to fabric type, we can use tape made out of either Fabric + Ethylene Vinyl Acetate Copolymer (EVA) or Poly Ethylene (PE) + EVA.
  • Application of tape should be outside surface of seam depending on fabric characteristics (usually on the coated side of fabric which should be outside).
  • A typical two layer seam sealing tape should have total thickness of 0.15 mm, weight of approximately 0.95 gm/square cm and inner layer melt index (ASTM D1238) of 200 gm/10 min. The seam sealing tapes are multi-layered adhesive films and are applied to the sewn seams to prevent water from leaking through those seams.The tapes are available in different widths & most commonly used width for PPE ranges from 18 ~ 20mm. Length : – 200m / roll

Classical Method of Manufacturing PPE