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Sheet 31Mix-up sheet · Silica, lead, chemicals and industrial hygiene

Silica Table 1: water, shrouds and the 4-hour line

Under 29 CFR 1926.1153, OSHA's construction silica standard, every employer with exposed workers keeps a written exposure control plan: the dusty tasks, the controls on each one, the housekeeping, and how access to the work is limited. Table 1 of the standard fills in most of that plan, because a listed task done exactly as the table says needs no air sampling at all.

Four terms the standard is built on

Table 1
The list in 1926.1153(c) that pairs common tasks (sawing, drilling, grinding, chipping, tuckpointing and others) with an engineering control, a work practice and, where needed, a respirator. Credit comes only when every part of the entry is fully and properly implemented.
Action level
25 µg/m³ as an 8-hour time-weighted average (TWA), half the PEL. On the measuring route, results between the action level and the PEL mean monitoring again within six months; results above the PEL, within three.
The 4-hour line
Table 1 splits its respirator column by how long one worker does the task in a shift: 4 hours or less, or more than 4. Where a respirator is listed, an assigned protection factor (APF) of 10 is the entry that appears most often.
Competent person
Designated under 1926.1153(g)(4) to make frequent and regular inspections of job sites, materials and equipment so the written plan is actually carried out. The competent person vs qualified person sheet covers what the title takes.

Dust decisions

Each card puts a crew on a cutting, drilling or siding job and asks what the standard expects of the supervisor before and during the work.

Card 1 of 6 · 0 right

Card 1

A laborer cuts concrete block outdoors for 5 hours in one shift using a handheld saw with integrated water delivery. Under Table 1 of OSHA's silica standard, what is the MINIMUM respiratory protection required?

Pick an answer. A short note for each option, A to D, appears here.

Card 2

A crew is cutting control joints in a slab with a walk-behind saw. Which dust control does Table 1 of OSHA's silica standard specify for this task?

Pick an answer. A short note for each option, A to D, appears here.

Card 3

A crew is using a water-fed saw from silica Table 1, but the water flow is set so low that visible dust still comes off the blade. What should the supervisor conclude?

Pick an answer. A short note for each option, A to D, appears here.

Card 4

After concrete is cut indoors, a laborer picks up a push broom to sweep up the dust. What cleanup method should the supervisor require instead?

Pick an answer. A short note for each option, A to D, appears here.

Card 5

A crew will drill dozens of anchor holes in a concrete wall with handheld rotary hammers. Which control should the supervisor put in place to BEST reduce respirable silica exposure?

Pick an answer. A short note for each option, A to D, appears here.

Card 6

A siding crew will switch from hand-scoring to power-saw cutting of fiber-cement panels, which creates silica dust. Which document should the supervisor update BEFORE the new work starts?

Pick an answer. A short note for each option, A to D, appears here.

    Where a crew drops off the table

    The standard has a front door. It does not apply where exposure stays below 25 µg/m³ under any foreseeable conditions, which is why short, wet or outdoor work sometimes falls outside it entirely. Once a task is in, the only question is which route it is on.

    Table 1 credit lasts only while the control works. A shroud whose vacuum hose has split, a dust collector with a full bag or a clogged filter takes the task off the table, and the employer is back to proving exposure some other way.

    Hours add up across tasks. When one worker does more than one Table 1 task in a shift and the combined time passes 4 hours, the respirator entry for more than 4 hours applies to each of those tasks, even if no single task ran that long.

    Cleanup has its own limits: no dry sweeping, dry brushing or compressed air where they could add to exposure, unless nothing else is feasible. Medical surveillance follows respirator use. A worker required to wear one on 30 days or more in a year is offered a baseline exam within 30 days of assignment and a repeat every 3 years.

    Tasks missing from the table go through an exposure assessment, and the fix runs in the order of the hierarchy of controls: engineering and work-practice controls first, respirators for whatever exposure they leave. Silica sits beside lead, solvents and welding fume on the silica, lead, chemicals and industrial hygiene sheet; the labels and safety data sheets on bagged cement, mortar and grout are covered under HazCom, SDS and labels. The full text is at 29 CFR 1926.1153 on osha.gov.

    What the written exposure control plan covers

    • Every task in the work that involves exposure to respirable crystalline silica
    • The engineering controls, work practices and respirators used for each of those tasks
    • The housekeeping measures used to limit exposure
    • How access to work areas is restricted, when needed, to keep the number of exposed workers and their exposure down, including exposure created by other employers' work

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