The Hierarchy of Controls on a Service Call

Why this matters

Most shops handle an exposure the same way: hand the tech a mask, a pair of plugs and gloves, and call it covered. That is the least reliable control there is, and it is the one every regulation and every research agency puts last. The hierarchy of controls is the order in which you look for a way to deal with a hazard, from the control that removes it to the control that only puts a barrier on the person. It costs nothing to run through on the drive over, and on a service call it usually turns up a cheaper and more reliable answer than the respirator. This card owns control selection for the library's exposure articles.

The five levels, and the question each one asks

NIOSH publishes the hierarchy in this order. Each level asks a different question, and you work down the list until you reach a level that is feasible for this job, then keep layering the levels below it as needed.

1. Elimination: does the hazardous task have to happen at all? Route a refrigerant line set through the rim joist above grade instead of coring the foundation. Use an existing cleanout instead of breaking the slab for a new one. Mount a bracket on the framing instead of drilling into the brick veneer. A hazard that never happens needs no other control.

2. Substitution: can a less hazardous material or method do the same job? A snap cutter or a wheel cutter on cast iron instead of an abrasive saw, which removes the spark shower and most of the dust. A water-based cleaner instead of a solvent degreaser. A battery tool instead of a gasoline engine in a basement. A mechanical drain cleaner instead of a chemical opener. Substitution is where you check the replacement does not bring a new hazard of its own; a citrus degreaser is gentler on the lungs than a chlorinated solvent and is still a skin sensitizer for some people.

3. Engineering: can the hazard be captured, isolated or diluted at the source, without depending on anyone's behavior? Water fed to the blade of a saw. A shroud on a grinder connected to a vacuum with a high-efficiency filter. A fan exhausting a closet to the outside while solvent cement cures. A barrier sheet and negative air on a dusty room. The defining property is that the control works whether or not the person remembers it, as long as it is set up and running.

4. Administrative: can you change how, when, or by whom the work is done? Schedule the dusty step when the family is out. Limit one person's hours on the loud tool and rotate. Keep the homeowner and the other trades out of the work area. Train the crew, post the sign, write the procedure. These all work only as well as people follow them, every time.

5. Personal protective equipment: what barrier goes on the person? Respirators, hearing protection, gloves, eye and face protection, coveralls. PPE protects only the person wearing it, only when it fits and is worn correctly, and fails without telling anybody.

Why PPE is last, as mechanisms rather than a slogan

Putting PPE last is not a judgment that it is useless. It is a statement about how each control fails.

• It fails silently. A respirator with a broken seal at the chin, or an earplug that backed halfway out, looks exactly like one that works. A shroud with a disconnected hose throws a visible cloud.
• It protects one person. The homeowner in the next room, the helper holding the light, and the child who comes home to dust on the stairs get nothing from the tech's respirator.
• It needs a program to work at all. A tight-fitting respirator worn as a requirement needs medical evaluation, fit testing and training under a written program per 29 CFR 1910.134, and annual fit testing at 1910.134(f)(2). Without that, a respirator is a reassurance, not a control. See related: OSHA Respiratory Protection - Annual Fit Test.
• The law puts it there too. 29 CFR 1910.134(a)(1) states that engineering controls are to be used as far as feasible, with respirators where effective engineering controls are not feasible or while they are being put in place. The noise standard at 1910.95(b)(1) asks for feasible administrative or engineering controls before relying on protectors once the permissible level is exceeded. In construction the respiratory requirement reaches through 29 CFR 1926.103, which incorporates the same 1910.134 program.

Engineering beats administrative for the same reason

An administrative control is a promise. "Nobody grinds for more than two hours" holds on the day the lead is watching, and slides on the day the job runs long and the second tech is out sick. An engineering control on the tool runs the same way at hour one and hour six. That is why the order holds even where the administrative fix looks easier: the easy fix is the one most likely to quietly stop happening.

The flip side is that an engineering control has to be maintained to keep its place in the order. A dust extractor with a loaded filter, a water feed with a clogged line, or a shroud with a cracked skirt is still on the tool and no longer doing the job. Engineering controls earn their rank only while they are verified working.

A worked call: one job, three exposures, walked down the list

A plumber is replacing a cracked section of cast-iron drain and adding a cleanout in a 1950s house with a finished basement. The plan as first written is: break about a 2 ft by 3 ft opening in the slab with an electric chipping hammer to reach the line, cut out the cracked cast-iron section with an abrasive saw, and glue in PVC with solvent cement inside a small utility closet. Three exposures come out of that plan: respirable silica from the slab, noise from the chipping hammer and saw, and solvent vapor in a closed closet, plus lead if anyone heats or saws the old lead-caulked hub joints.

Silica from the slab. Elimination first: is there another way to the line? The basement has an existing cleanout upstream, but the crack is between it and the stack, so the slab has to open. No substitute for breaking concrete exists here. Engineering: the chipping hammer runs with a commercially available shroud and a vacuum meeting the dust-collection requirements, or with water at the point of impact. Under the construction silica standard's Table 1 row for jackhammers and handheld powered chipping tools, the task done indoors calls for a respirator with an assigned protection factor of at least 10 on top of that control, regardless of how long the task runs. So this is a case where PPE is required in addition to engineering, not instead of it. Administrative: the family stays upstairs with the basement door shut, and the opening gets HEPA-vacuumed, not swept. See related: Respirable Crystalline Silica and the Construction Standard, and How to Follow Table 1 When You Core or Grind Concrete.

Lead at the hub joints. Elimination: nobody melts the lead out of the old joints with a torch, which removes the fume route entirely. Substitution: a snap cutter cuts the cast iron cleanly a few inches back from each hub, so the abrasive saw never touches a lead-caulked joint and never throws metal dust. The cut-out hubs go into a bag whole. What remains is a skin and ingestion route from handling the old joints: gloves, and hands washed before eating or getting into the truck. See related: How to Keep Lead From Coming Home on You.

Solvent vapor in the closet. Substitution: a low-VOC solvent cement listed for the pipe material, where the local plumbing code as adopted by your jurisdiction accepts it, reduces the vapor load without changing the joint. Engineering: a box fan in the closet doorway pushes the closet air toward an opened basement window, set up before the can is opened rather than after the smell builds. Administrative: one can open at a time, lid on between joints. PPE: nitrile or other gloves the cement's SDS names, because the solvents absorb through skin and the vapor route is not the only one. See related: Adhesive and Sealant Vapors in Tight Spaces.

Noise. The chipping hammer is the loudest tool on the job. There is no quieter way to break this slab that is practical here, so the controls are administrative and PPE: the chipping runs in short blocks rather than one long stretch, and the operator and anyone in the basement wear hearing protection fitted properly. See related: How to Fit Earplugs So They Actually Work.

What the walk changed. The first plan relied on a dust mask and whatever was in the truck. The revised plan removed the lead fume entirely (no torch, no saw at the hubs), replaced the abrasive saw with a snap cutter, put a shroud and vacuum on the chipping hammer, added an APF 10 respirator only where the standard requires one, ventilated the closet before the cement came out, and kept three people out of the basement. Two of the four exposures, lead and solvent, were reduced at the first two levels, not the last. The time cost was about 20 minutes of setup on a job of roughly 5 hours, which is under a tenth of the job.

What changes the order of the search

• The tool is not on the truck. If the shroud and vacuum are back at the shop, the honest answer is to reschedule the dusty step, not to substitute a mask for the missing control. An administrative or PPE control filling in for a missing engineering control is the hierarchy running backwards.
• The occupant changes the stakes. An infant, a pregnant occupant, or someone on oxygen in the house moves elimination and isolation to the top of the conversation, because PPE on the tech does nothing for them, and OSHA does not reach the customer at all. Your duty to the occupant is the ordinary duty of care, which is a reason to plan, not a regulation to cite.
• A substitute brings its own hazard. Switching a dry cut to a wet one with a corded tool adds an electrical hazard: use a tool built for wet cutting, on a GFCI-protected circuit, with the cord routed away from the water.
• The control has to be shown to work. A shroud and vacuum on a grinder is engineering only if the vacuum meets the airflow and filter requirements of the task and is drawing. Check for visible dust at the shroud skirt in the first minute of the cut.

Where the hierarchy gets misused

• "We supply PPE" offered as the whole plan. It is the last level, and in most standards it is required to be backed by a program.
• An administrative control with no owner. A rule that someone limits their hours is only real if someone tracks the hours.
• Calling a dust mask a respirator. A loose-fitting dust mask is not a respirator for a respirable hazard, and wearing one voluntarily still carries duties for the shop. See related: Voluntary Respirator Use and What the Shop Still Owes.

References

• NIOSH, Hierarchy of Controls, for the five levels and their order.
• 29 CFR 1910.134(a)(1) and (f)(2), engineering controls first and annual fit testing; 29 CFR 1926.103 for construction.
• 29 CFR 1910.95(b)(1), feasible controls for noise above the permissible level.
• 29 CFR 1926.1153, Table 1, for the jackhammer and chipping tool row used in the worked call.
• See related: Dose, Route, and the Exposure You Cannot See; How to Decide Whether a Task Needs a Respirator.