3M masks are characterized by the fact that they can be taken apart and that there are replacements for all parts, not just the replacement filters.
Class 1 filters: With half mask, it protects until 10xVLA or 1000ppm according to minor value; with full mask it protects until 200xVLA or 1000ppm according to minor value.
Class 2 filters: With half mask, it protects until 10xVLA or 5000ppm according to minor value; with full mask it protects until 200xVLA or 5000ppm according to minor value.