When it comes to chemical suit, seams are of utmost importance. There are various types of seam construction that provide varying degrees of protection.
Serged seam. Appropriate for low-level exposures, but not suitable for skin-absorbable or skin-toxic chemicals. A serged seam joins two pieces of material with a thread stitch that interlocks. It is typically used on limited-use clothing where dry particulates, non-toxic dirts, dusts and a low concentration of residual contamination are involved.
Bound seam. The next level up, this is a serged seam with material folded over the edge and sewn on for a higher degree of protection against liquids and dry particulates. The seam is chain stitched through all of the layers for a clean finished edge.
Ultra-sonic seam. Offering yet a higher level of protection, this is a seam without thread - no holes are sewn. Used widely in the medical field and to a lesser degree in the industrial arena, this seam can be liquid-proof and is good for higher splash exposure.
Heat-sealed seam. The highest performing and highest cost seam, this seam is sewn and then hermetically sealed with a thermally welded seam tape. The impervious seal provides a liquid-proof seam and should be used when working with a high concentration chemical. Heat-sealed seams are well suited for Level A and B chemical protective clothing.