Concrete Floor Grinders & Shot Blasters

Floor grinders and shot blasters prepare concrete floors by grinding, polishing and removing coatings. They produce huge amounts of fine dust that contains respirable crystalline silica, and they are heavy, loud and powerful. Dust control, proper machine handling and hearing and respiratory protection are the keys to doing this work safely.

• Construction
• Concrete
• Flooring

Types of machines

• Walk-behind floor grinders use rotating diamond or abrasive discs to grind, level and polish concrete. Sizes range from small units to large, heavy machines with planetary heads.
• Handheld angle grinders with diamond cups handle edges and corners. See Angle Grinders.
• Shot blasters throw steel shot at the floor to clean and profile it. The shot is recycled, and the dust is collected.
• Scarifiers and planers use rotating cutters to remove coatings and rough up surfaces.
• Power: electric (corded) machines, battery machines, and propane or gas-powered machines.
• Floor grinding may be dry (with dust extraction) or wet (with water).

Main hazards

• Silica dust: grinding concrete creates respirable crystalline silica, which causes silicosis, lung cancer, kidney disease and COPD. Without controls, a grinder can create a visible cloud and hazardous exposures within minutes. See Silica.
• Dust from coatings: old paint, mastic and adhesives may contain lead or asbestos, which can be released when ground. Test before you grind. See Lead and Asbestos.
• Noise: grinders and shot blasters are loud, often over 90 decibels. See Noise.
• Vibration from handheld grinders. See Hand-Arm Vibration.
• Machine hazards: large machines are heavy, can tip, pull the operator, trap feet or catch cords. Rotating discs and shot are hazards in themselves.
• Electrical: cords, wet conditions and GFCI problems. See GFCI and Wet Locations.
• Carbon monoxide from propane or gas-powered machines indoors. See Carbon Monoxide.
• Slips and trips from slurry, cords and hoses.
• Lifting and loading heavy machines and discs. See Lifting & Ergonomics.

OSHA’s silica rule for grinders

• OSHA’s respirable crystalline silica standard for construction (29 CFR 1926.1153) sets a permissible exposure limit of 50 micrograms per cubic meter over 8 hours, and an action level of 25. Employers can follow Table 1, which lists the controls and respirators for common tasks, or measure exposures.
• Table 1 includes entries for handheld grinders and for walk-behind equipment used on concrete. In general, it calls for water delivery to the cutting surface or a dust collection system with a HEPA filter, and sometimes respirators depending on the task, setting and duration. Check the actual table for your equipment and conditions.
• Employers must also have a written exposure control plan, a competent person, training and medical surveillance for workers who wear a respirator 30 or more days a year, and housekeeping rules that ban dry sweeping and compressed air. See Medical Surveillance Requirements.
• If the work isn’t covered in Table 1, employers must assess exposures and control them.

Dust control in practice

• Wet grinding: a water feed keeps dust down. It makes slurry that must be controlled, collected and disposed of properly. Keep slurry out of drains. See Stormwater & SWPPP.
• Dry grinding with a dust shroud and a HEPA vacuum or dust extractor: use a shroud that fits the machine, a vacuum with an adequate airflow rating, a HEPA filter and a pre-separator or cyclone for heavy loads. Keep hoses short and unkinked, and empty and clean filters on schedule. See Dust Extractors.
• Check the system before every shift: make sure the shroud seals against the floor, the hose is connected and airflow is strong. Fix leaks, and stop work if dust escapes.
• Isolate the work area: use plastic barriers, negative air machines and signs, and keep others out. Close doors and vents so dust doesn’t spread to occupied areas.
• Respirators: wear a respirator when Table 1 or your exposure assessment calls for it. Make sure it is fit tested, with workers medically cleared and trained. See Respiratory Protection, Respirator Filters and Fit Testing.
• Clean up using a HEPA vacuum or wet methods. Never dry sweep or blow dust with compressed air.
• Wash up and change clothes before leaving. See Take-Home Contamination.

Running the machine safely

• Read the manual and get trained on the specific machine. Check controls, emergency stops and safety features such as a deadman handle.
• Inspect before use: check the discs and tooling for wear and damage, bolts tight, guards and skirts in place, cords undamaged and hoses connected.
• Handle large machines carefully. A heavy planetary grinder can pull and spin. Keep a firm grip, stand in a stable stance, avoid sudden changes and keep feet and cords out of the way. Use a ramp or lift gate and enough people to load and unload.
• Mind the electrical supply. Use heavy-duty, correctly sized cords, GFCI protection and lockout for service. Don’t run cords through slurry.
• Propane and gas machines: use only in well-ventilated areas, with CO monitors, and handle cylinders safely. See Propane.
• Watch for obstacles such as anchor bolts, rebar, embedded metal and expansion joints that can snag or kick back the machine.
• Shut off, unplug and let discs stop spinning before changing tooling or cleaning. See Lockout/Tagout.

Shot blasting specifics

• Keep the blast chamber and skirts sealed so steel shot and dust don’t escape. Shot on the floor is slippery, and flying shot injures eyes and skin.
• Keep people clear of the machine’s path and out of the room, and wear hearing, eye and respiratory protection.
• Collect spent shot and dust in a closed system, and dispose of waste properly.

Fire, dust and noise

• Dust from coatings, adhesives or wood can burn, and sparks from steel discs or shot can ignite flammable vapors from adhesives and solvents. Keep flammables out. See Flammable Liquids.
• Wear hearing protection and monitor noise levels. See Hearing Protection.
• Wear safety glasses, a hard hat if needed, safety boots and gloves suited to the work. See Eye & Face Protection and Foot Protection.

Floor grinding checklist

• Floor and coatings tested for lead and asbestos; exposure control plan in place
• Water feed or a sealed HEPA dust collection system working on every machine
• Work area isolated; no dry sweeping or compressed air; HEPA vacuum for cleanup
• Respirators, hearing and eye protection worn; workers trained and medically cleared
• Cords on GFCI; propane machines used with ventilation and CO monitors
• Machines inspected; tooling changed only with the machine locked out

Last updated: October 4, 2026