In general usage of approved material and right process, flow are important in the manufacturing process of Personal Protective Equipment (PPE). AAMI Level 4 equivalent viral & blood penetration resistance are required for medical workers who are in the front line fighting Coronavirus 2019-nCov
 
The classic method of joining fabrics is by the process of sewing, which results in needle penetration holes along stitching seam, it is mandatory that both fabric and seam are compliant to ISO 16603 / ASTM F1670 (resistance to synthetic blood and body fluid infiltration) and ISO 16604 /ASTM F1671 (resistance to viral infiltration) standards. Among these standards, ISO 16604 test is generally considered as the important in compliance requirement. For test analysis, the bacteriophage used is (0.027 microns) and Coronavirus 2019-nCoV is 0.125 microns. Hence passing the ISO 16604 test class is a good indicator that fabric and seam are unlikely to allow the virus to infiltrate.
 
There are two different type of PPE , Gowns and Coveralls ( Hazmat Suits). We will consider coveralls to explain the process and will also establish the process of Gowns also. Coveralls are generally a hooded top attached with trouser at waistband. There are two ways of making Hazmat Suits AAMI 4 level compliant.
 
1.    Fabric can be attached together by either traditional method (traditional stitching) and then seams are sealed by tapes.
2.    Ultrasonic welding
 
Preferred way of making Hazmat Suits AAMI 4 level compliant is Stitching Method 

Stitching Method 
 
Stitching can be done by Single Needle lockstitch and 4 Thread Overlock depending on the seam joining requirement, then the Seam Sealing can be done by using adhesive tape and hot air seam sealing machine. The adhesive tape in the process is a consumable like thread in stitching process. The heated tape and the fabric are feed into two rollers rotating in opposite direction under controlled pressure  The multi-layered sealing tapes are adhesive films and are applied to the sewn seams to prevent water from leaking through those seams.
 
For Hazmat Suits/ Coveralls a dual layer adhesive tape can be used, which are designed to seal seams on light to medium weight, PPSB( Spun Bond Polypropylene) . A typical dual layer seam sealing tape needs to 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.