OSHA's silica standards use two filter ratings for vacuums: a dust collector with 99% or greater filter efficiency, and a HEPA filter that is at least 99.97% efficient at 0.3 micrometers. Each task specifies one of the two.

The rating decides which vacuum a crew may use for a given task. If the crew uses a 99% unit where the standard names HEPA, the task is not done as Table 1 specifies. A HEPA unit bought for a task that calls only for 99% exceeds the requirement. Neither rating replaces the other in the text of the rule.

Last updated: October 3, 2026.

How the two ratings work

The construction standard, 29 CFR 1926.1153, defines a HEPA filter as one that is at least 99.97% efficient at removing mono-dispersed particles of 0.3 micrometers in diameter. A filter that does not meet that figure at that particle size is not HEPA under the standard.

The standard sets a separate, lower figure for dust collection systems used for capture at the source on Table 1 equipment. These systems must have a filter efficiency of 99% or greater. This figure is not tied to the 0.3 micrometer test particle in the HEPA definition.

A spec sheet can therefore state one of two things:

  • A HEPA claim. The filter is rated at 99.97% or higher at 0.3 micrometers. This meets both ratings.
  • A percentage alone, such as 99%. This meets the dust collector rating. It does not show that the filter meets the HEPA definition.

According to OSHA's construction guidance, an employer may rely on the manufacturer's representation of HEPA efficiency. The employer does not have to test the filter independently. Any HEPA rating on a product is the maker's claim.

Tasks that name each rating

Task or provision Filter the standard names Source
Cleaning holes drilled with handheld or stand-mounted drills HEPA (99.97% at 0.3 micrometers) 1926.1153, Table 1
Removing loose dust between passes, walk-behind milling machines and floor grinders, indoors or in enclosed areas HEPA 1926.1153, Table 1
Dust collection systems on Table 1 equipment 99% or greater filter efficiency 1926.1153, Table 1
Handheld grinders used for mortar removal (tuckpointing) 99% or greater, plus 25 cfm or more of airflow per inch of wheel diameter 1926.1153, Table 1
Housekeeping cleanup in place of dry sweeping HEPA-filtered vacuuming named as an alternative 1926.1153(f); parallel provisions in 1910.1053

Drilling. The Table 1 entry for handheld and stand-mounted drills states: "Use a HEPA-filtered vacuum when cleaning holes." This applies to the cleanout step after drilling.

Milling and floor grinding indoors. Loose dust between passes must be removed with a HEPA-filtered vacuum when the machine is used indoors or in an enclosed area.

Tuckpointing. The collector needs 99% filter efficiency and an airflow figure. If a grinder has a 5-inch wheel, the minimum airflow is 5 × 25 = 125 cfm. That example is hypothetical. The airflow figure is set by the standard.

Housekeeping. Section (f) of the construction standard states: "Employers shall not allow dry sweeping or dry brushing where such activity could contribute to employee exposure to respirable crystalline silica unless wet sweeping, HEPA-filtered vacuuming or other methods that minimize the likelihood of exposure are not feasible." OSHA states that the general industry and maritime standard, 29 CFR 1910.1053, contains parallel requirements.

What it is not

"HEPA everywhere" is not the rule. Some compliance blogs describe grinder dust collectors as needing a HEPA filter. The text of 1926.1153 states 99% or greater filter efficiency for Table 1 dust collection systems. HEPA is named for hole cleaning, for dust removal between passes indoors, and for housekeeping.

A 99% rating is not "nearly HEPA." The HEPA definition sets both an efficiency and a particle size. A 99% figure with no particle size does not meet that definition.

A HEPA filter is not a full control. Table 1 pairs each vacuum with other conditions, such as shrouds, airflow, work practices and, for some tasks, respirators. A compliant filter alone does not satisfy the Table 1 entry.

Using this when buying or auditing

List each silica task the crew performs. For each task, find the filter the standard names:

  • If the task is cleaning drilled holes, a HEPA vacuum is required.
  • If the task is indoor milling or floor grinding, a HEPA vacuum is required for removing dust between passes.
  • If the task is dry cleanup that would otherwise be swept, HEPA-filtered vacuuming is one of the named methods.
  • If the vacuum serves only as a dust collector on Table 1 equipment, 99% filter efficiency meets the text. For tuckpointing grinders, the airflow figure also applies.

One HEPA unit can serve every task above. A 99% unit can serve only the collector tasks.

Check the spec sheet for 99.97% at 0.3 micrometers before relying on it as HEPA. Record the vacuum assigned to each task in the written exposure control plan, with its housekeeping method.

The research for this page does not include manufacturer filter specifications for individual vacuum models. This page therefore does not name units that qualify. The maker's published rating is the document to check for any model.

Table 1 is one of two compliance paths. The other is exposure assessment. The PEL and compliance paths are covered separately. Under 1926.1153 the PEL is 50 µg/m³ as an 8-hour time-weighted average, and the action level is 25 µg/m³.