Daily Code Talk #77: IMC 510 Part 3 (510.1.3 Exhaust Discharge + Recirculation)

🧠 Plain-English Highlights• Default rule: discharge to outdoors- Dust/stock/refuse conveying exhaust must discharge to the exterior, either:1. Directly by flue, or2. Indirectly through the bin/vault the system discharges into, unless contaminants are removed.• Recirculation is allowed only with strict conditions- You can recirculate exhaust air only if ALL of the following are met:1. Particulate removal: minimum 99.9% at 10 microns.2. Vapor safety: vapor concentrations are < 25% of the LFL.3. Monitoring: approved equipment continuously monitors vapor concentration.🏗️ Why it mattersCommon failure: “recirculating dust collector” shown with no performance basis, no LFL monitoring callout, or no clear statement of where the air actually discharges.🗺️ Where to show it• M-001: indicate DISCHARGE TO OUTDOORS or RECIRCULATION PER 510.1.3 with the three criteria.• Schedules: call out filtration efficiency (99.9% @ 10µm), monitoring device type/location, and alarm/shutdown sequence (if specified by the manufacturer/AHJ).• Plans: show discharge path (flue vs bin/vault) and equipment locations.✅ Do• Default to 100% exhaust to outdoors unless you can document all 3 recirc criteria.• Call out 99.9% @ 10µm on the equipment schedule and submittal basis.Show the vapor monitor (location + alarm/shutdown sequence if required by mfr/AHJ).• Make discharge intent obvious: “DIRECT OUTDOOR DISCHARGE” or “RECIRC AIR.”⛔ Don’t• Don’t label a unit “recirculating” without stating 99.9% @ 10µm and <25% LFL.• Don’t omit the approved vapor concentration monitoring callout.• Don’t leave discharge routing ambiguous (field will assume the easiest path).• Don’t treat dust conveying exhaust like “general return air.”🔧 Field tipUse the “3-PART RECIRC CHECK” during review:99.9%@10µm + <25% LFL + approved monitor.If any one is missing → EXHAUST TO OUTDOORS.Comment “IMC510-P3” if you want a paste-ready M-001 note + a schedule line item for recirc criteria.