or scum (mainly oxides and impurities) forming
on the surface
molten metals, as they are being melted or refined.
(4) Individual constituent testing. Because of the varying factors when
arc-welding and the varying fumes are produced, the fumes must be frequently tested
for the presence of individual constituents to determine if specific threshold limit value
has been exceeded. When arc-welding steels, for example, testing should be
conducted on the fumes to determine if a hazardous form of hexavalent chrome (CrVI)
(a chrome compound) is present and registering above the TLV. Some hexavalent
chrome compounds are carcinogenic, especially water-insoluble ones. Because the
TLVs vary with the compounds present for chrome and their chrome compounds,
analysis of the fumes for hexavalent, and total chrome are needed.
NOTE: Variable concentrations of a wide variety of substances are found in the work
place air. Two organizations promulgate standards for worker exposure to specific
chemicals. In Title 29 Code of Federal Regulation 1910.1000, OHSA has established
Permissible Exposure Limits (PEL'S) for potentially hazardous chemical substances.
The American Conference of Government Industrial Hygienists (ACGIH) has
recommended threshold limits (TLV) which do the same. Ordinarily, ACHGIH TLVs are
more stringent (and provide greater worker protection) than OSAH PELs. It is important
to understand that PELs and TLVs is not the same thing.
(5) Total fume concentration or content analysis. Analyze the total fume
concentration or content as needed. This analysis will be sufficient if no other toxic
elements are present in the metal, welding rods, or metal coatings and conditions are
not ripe for toxic gas formation.
The U.S. Army must comply with the standards of 29 CFR l9l0.l000 for
exposures to airborne contaminants. In addition, the Army has adopted the consensus
standards developed by the ACGIH. We must check both sources and use the more
stringent of the two standards.
a. Standards. The standards in 29 CFR l9l0.l000 are termed Permissible
Exposure Limits (PELS) while those from ACGIH are TLVs. Whatever they are called,
they represent the maximum amount of chemicals under which it is believed that nearly
all workers may be repeatedly exposed day after day without adverse effect. The TLV
booklet is a consensus standard published by a civilian organization. They are updated
annually to reflect current data. The TLV booklet is the most common and current
source of standards for airborne contaminants. Appendix C contains industrial hazards
found in the Army.