Polishing a slab inside a building that stays open to staff, tenants or customers turns the job into an indoor air quality exercise. Most complaints come from dust on corridors, clothing and air returns, not the finish, so the plan starts with zoning, containment and extraction rather than grit sequence. This article covers enclosure and negative pressure, dust capture, readiness checks, scheduling and the dispute record trail. Figures are planning targets; limits follow the specification and local silica regulations.

Why occupied-building polishing carries a different dust risk

Grinding and polishing releases respirable dust, including crystalline silica, from paste and aggregate. Metal phases at 16/20/30/40 grit remove the most material; resin phases at 100/200/400/800/1500/3000 grit produce finer dust that stays airborne longer. In an open occupied space that dust reaches offices and returns within minutes; in a sealed enclosure with extraction it is captured at the shroud. Walk the floor with the owner rep before pricing and mark spaces that cannot accept even a light dust film.

Enclosure zoning and negative pressure setup

Divide the slab into work and buffer zones before tooling arrives. A typical enclosure uses 2.0-2.4 m tall plastic sheeting on stud or zipper frames, sealed to floor and overhead; doors get a zipper entry or double-door air lock. Keep the occupied side at higher pressure: the zone runs at negative 5 to 10 Pa, so air leaks inward. Use one HEPA H13 extractor per machine and target 12-15 air changes per hour.

• Zone pressure: negative 5 to 10 Pa vs the occupied side, checked with a manometer at the door.
• Air change: 12-15 ACH inside the enclosure, confirmed with a smoke pencil at gaps and seams.
• Filter class: HEPA H13 or better; inspect the filter label and door seal before start-up.
• Enclosure seal: 2.0-2.4 m sheeting sealed to slab and overhead; re-tape gaps at joints and penetrations.
• Air returns: isolated or redirected during works, reviewed with the building engineer.

Dust extraction and wet dust control during grinding

Dry grinding with a shrouded machine and HEPA extractor is the default where the slab stays dry. Keep the shroud 2-5 mm off the slab each pass; check that shoe wear has not lifted the edge. Empty drums inside the enclosure, wet-wipe before removal, and seal waste in heavy bags. Wet suppression applies where dust escapes or heat control is needed: mist at the contact point rather than flooding, since standing water carries fines into joints. After wet passes, let the slab reach project moisture before densifier; surface temperature stays 10-30 C and RH below 75-80% for chemical work. Edge tools need their own small HEPA extractor; the 100-200 mm wall band is where complaints originate.

Fugitive silica controls during finishing and densifying

Once the slab moves to resin phases and densifier, dust drops but residue and odor remain. Apply densifier at the project dilution, commonly 1:64 (about 15 ml/L) neat and 1:128 (about 8 ml/L) ready-use; do not over-spray onto walls, stock or equipment. Clean daily: wet-mop or HEPA-wipe surfaces and ledges within 3 m; sweep only with a HEPA vacuum, never a dry broom. Inspect under 300-500 lux raking light for film, log each clean, and keep walk-off mats at the air lock.

Occupancy-readiness criteria: air, surface and odor

The floor cannot be handed back when grinding stops. Define the handover checks with the owner rep before work starts, and run them zone by zone against the basis below.

After densifier or sealer, keep extractor and make-up air running for the drying window in the spec, typically 12-24 h before normal occupancy, longer in sealed rooms with low air movement. Record temperature, RH and finish time of the last application so the handover date is defensible.

Scheduling windows and the agreement with the owner

Most occupied-site disputes come from unclear timing, not finish quality. Agree the window in writing before mobilization: grinding hours, whether weekend or night shifts are allowed, and how the owner notifies tenants. List adjacent spaces and their hours, agree start and stop times and overnight-shift lead time, define which doors and elevators carry equipment, and record who approves each handover. Noise follows the same zoning as dust; heavy metal phases are loudest, so warn next-door occupants and cover the travel path.

Complaint avoidance and walk-back points

Treat every complaint as a traceable event: time, location, what the occupant saw, who checked it and what was cleaned. Most early complaints are dust carried on boots or carts; checking walk-off mats and the air lock resolves them before escalation. Walk complaint routes before closure and wipe frames, sills and partition tops in the buffer; dust settles on edges a mop never reaches. Compare against baseline photos taken before mobilization.

Record-keeping and the handover package

The handover package lets the owner verify containment held and the slab met the agreed finish. Keep pressure readings, filter changes, clean sign-offs, moisture and slip tests, and the final walk-through; include the grit sequence run, densifier dilution and deferred items with their date. If a zone opens early for inspection, return it to containment and repeat the dust check. A clean walk-through protects both sides: controlled delivery on one side, a documented baseline against later wear or stain claims on the other.