Fume Hood Replacement Guide: Swap, Upgrade or Redesign
Replacing a fume hood is rarely a simple swap. This guide covers how to evaluate the old hood and exhaust system, choose the right liner material, and coordinate the project so the new hood actually matches how the lab uses it today.
Signs a Fume Hood Needs Replacement
Most replacement projects start with one of a handful of observable problems. Knowing which one you have helps determine whether you need a straight swap, a liner-only repair, or a full redesign.
In-Kind Replacement vs. Redesign: Pick the Right Path First
The first decision on any replacement project is whether to duplicate the existing hood or re-engineer it to match current use. Institutional and government retrofit projects increasingly choose the second option, because the original equipment was often sized for a process that has since changed, or was undersized or oversized to begin with. Blindly copying an old schedule can carry the same problems forward.
Before you request a quote, decide which path fits your project. In-kind replacement is faster to specify but only makes sense if the original hood was correctly sized and the processes inside it have not changed. Redesign takes more upfront work but catches sizing errors, outdated utility lists and mismatched exhaust capacity before they get built into a new system.
On multi-hood retrofit jobs, it is common to find that hood schedules, utility lists and as-built drawings disagree with each other. If you have more than one source document (an old facilities list, a mechanical set, and a punch-list spreadsheet, for example), reconcile them before finalizing quantities. Treat old as-builts as a starting point to verify, not a final answer, especially if the hoods have been modified or added to over the years without updating the drawings.
What Data to Collect From the Old Hood and Exhaust System
A good replacement quote depends on accurate field data, not just a model number. Collecting this upfront avoids a round of corrections later, including the kind of quantity and configuration errors that show up when hood schedules are reconciled from multiple documents.
Walk the hood and exhaust path and record:
- Exterior hood dimensions (width, depth, height) and interior work surface size
- Sash type and opening height
- Duct collar size and location (top, rear)
- Make, model, and serial/data plate photo, if legible
- Current fan make, model, and rated CFM, plus its physical location (rooftop, penthouse, in-line)
- Static pressure readings if available, or at least duct length and number of turns from hood to fan
- All utilities currently piped or wired to the hood: gas, vacuum, air, water, electrical, and whether each is actually connected to a live line or just stubbed with a valve
- Whether the building has house vacuum, versus individual vacuum pumps needed under hoods with vacuum fixtures
- Photos of the hood interior, baffles, sash track, duct connection, and any visible corrosion or damage
- Any snorkels or local exhaust arms connected to the same duct run, and whether that ductwork is dedicated or shared with the fume hood
On older buildings, it is common to find snorkels that were added after the original design and tied informally into lightly used fume hood ductwork, with no dedicated ductwork of their own. If that is the case here, plan for new snorkel infrastructure as part of the project rather than assuming the existing duct run has spare capacity. Our exhaust snorkel sizing guide and mounting and clearance guide cover how to size and place these correctly rather than piggybacking on hood ductwork.
Choosing Liner and Material Grade for Acid and Corrosive Work
Material grade mismatches are one of the most common causes of premature liner failure, and one of the hardest to diagnose after the fact. Stainless steel is not one material. Grades like 304 and 316 behave very differently with certain acids, and neither is the right answer for every application.
If you are seeing corrosion and suspect the wrong grade was installed, document the chemicals actually used in the hood (ask lab staff, do not assume from the original design intent), the age of the hood, and where on the liner the damage appears. Corrosion that starts at the baffles and spreads forward often points to vapor attack from acid fuming rather than splash damage, which is a different failure mode than a spill. This kind of documentation is also what you will need if there is an internal cost dispute over who specified the original material.
Perchloric acid and hydrofluoric acid are special cases. Perchloric acid requires a dedicated wash-down hood system, not a standard fume hood, because dried perchlorate residue in ductwork is an explosion hazard. Hydrofluoric acid attacks glass and many standard liner materials and typically needs a polypropylene or PVC liner rather than coated steel or standard stainless. If either chemical is used or may be used in the future, flag it early. Ask us which liner and hood construction fit your specific acid list. Do not assume a general-purpose acid-resistant hood covers these two chemicals.
Exhaust Fan, Static Pressure and HVAC Coordination
Hood-level airflow requirements are the starting point for fan sizing, but they are not the whole picture. Someone needs to account for duct routing, turns, and losses between the hood and the fan, and that is a mechanical engineering task, not a hood selection task.
We can tell you the rated CFM a given hood needs at the face. Your mechanical engineer or HVAC contractor needs that number, plus duct length, turns, and any shared ductwork, to size or confirm the fan and verify static pressure across the whole run. On replacement projects, loop in your engineer early so the fan and rooftop infrastructure are sized for the hoods you are installing, not just matched to the old fan’s nameplate.
If the project is replacing fans or rooftop curbs along with hoods, confirm whether you are keeping the same footprint (same curb, same duct collar location) or changing it.
Coordination deadlines are often tighter than the rest of the project. If HVAC or mechanical contractors need hood dimensions and CFM before a drywall milestone, send us what you have (even a tentative hood list) so we can return usable numbers quickly. Confirm minor details like cabinet configuration afterward.
Compare ducted, ductless, biosafety and specialty hoods on our main laboratory fume hoods page.
NFPA 45, Classified Locations and Explosion-Proof Questions
Whether a hood or room needs NFPA 45 provisions, classified-location wiring, or explosion-proof construction is a determination made by your engineer of record, electrical engineer, and authority having jurisdiction, not by a furniture or hood supplier. We build to the specification you give us; we do not make the classification call.
This question comes up often when a process can release a flammable gas, such as methane from wastewater or biological samples, even if the primary use of the hood is not flammables handling. If there is any chance of that happening in your process, raise it with your electrical engineer and AHJ before finalizing hood specifications. Explosion-proof construction changes the hood, lighting, and electrical scope materially, so it is worth resolving early rather than after equipment is ordered.
General reference: NFPA 45 covers fire protection for laboratories using chemicals, and classified-location requirements come from NFPA 70 (the National Electrical Code) based on what hazardous materials are present and how. Confirm the specific requirements that apply to your room and process with your engineer and local fire/building officials. Do not rely on a hood spec sheet alone to determine this.
Permitting, Documentation, Removal and Building Coordination
On replacement projects inside occupied or active buildings, the hood itself is often the easiest part. Permitting documentation, old hood removal, and coordinating with unrelated facility work tend to cause more delays.
Who typically handles what
| Task | Typically owner/engineer responsibility | How we can help |
|---|---|---|
| Permit applications and plan check submittals | Owner or project engineer/architect of record | We can provide dimensions, specifications and product documentation for your submittal |
| Hazardous materials disclosure letters (e.g., for local fire department review) | Owner, based on actual chemical inventory | We do not generate these; we can confirm hood construction details referenced in your documentation |
| SDS for chemicals used in the hood | Owner/lab safety officer | Not provided by us; this is lab-specific chemical inventory information |
| Removal, decontamination, and disposal of the old hood | Owner, typically via EHS or a decon contractor before demo | We do not perform decontamination; confirm your decon protocol before removal crews arrive |
| New hood design, construction documentation, and specifications | Supplier | This is where we focus: drawings, dimensions, and material specs for your approval |
Decontamination before removal is the owner’s responsibility, and it has to happen before a crew physically removes the old hood. Build this into your schedule rather than treating it as something that happens the morning of demo.
Replacement projects rarely happen in isolation. It is common for a hood replacement to run into unrelated building issues discovered mid-project: a leaking roof, a sewer line that happens to run under the hood location, or a power grid upgrade the city is doing on its own schedule. None of these are hood problems, but they can delay or resequence the project significantly. Flag any known infrastructure issues (water damage, utility work, structural concerns) as early as possible so phasing can account for them, particularly in an occupied building where the lab may need to keep partially operating during construction.
What to Send Labs USA to Get an Accurate Quote
A fast, accurate quote depends on what you can share, not on having every detail finalized. Send what you have; we will flag what is still missing.
Photos and dimensions
Photos of the existing hood (interior and exterior), the data plate if legible, and your best measurements of width, depth, height, and duct collar location and size.
Chemical list
The chemicals actually used in the hood today, including acids, solvents, and anything requiring a specialty liner such as hydrofluoric or perchloric acid.
Utility and exhaust info
Current fan make/model and rated CFM if known, whether house vacuum exists, and any gas, air, or water connections at the hood.
Any existing schedules or drawings
Even conflicting or outdated hood schedules, mechanical drawings, or as-builts help us reconcile what is actually there versus what is on paper.
Project constraints
Known coordination issues: construction phasing, occupied-building limitations, NFPA or classified-location questions already raised by your engineers, and any hard deadlines like an upcoming drywall or submittal milestone.
You can start with our Fume Hood Configurator to rough in dimensions and configuration, or use the Lab Specification & RFP Analyzer if you already have a spec or hood schedule to reconcile. For broader renovation projects involving casework and work surfaces alongside the hood, our Lab Renovation Checklist and free lab design service can help you plan the full scope. Call (801) 855-8560 or send your photos and chemical list to get started; we will tell you what else we need.
Shop Filtered Fume Hoods Online
These ductless filtered fume hoods are related products, not a direct replacement for every ducted hood. Use them when your chemical list and EHS review support a filtered hood, or request a quote for a ducted replacement.
Get a free quote
Tell us about your lab, the equipment you need and your timeline. A Labs USA specialist will follow up with options and pricing. Prefer to talk? Call (801) 855-8560.
Fume Hood Replacement FAQ
Can I just order the same hood model to replace my old one?
Sometimes, but only if the original hood was correctly sized for your current processes and exhaust system. On many retrofit projects the old equipment was undersized, oversized, or built with the wrong liner material, so it is worth a quick review before duplicating it. Send us your dimensions and chemical list and we can flag anything that looks off.
How do I know if my fume hood liner is the wrong material grade?
Premature corrosion, especially near the rear baffles within a year or two of installation, often points to a liner material that does not match the chemicals used. Document which chemicals are actually used in the hood and where the damage appears, and ask us or your engineer to review it against the liner specification.
Who decides if my fume hood needs explosion-proof construction?
That determination is made by your electrical engineer, engineer of record, and the authority having jurisdiction, based on what hazardous materials may be present in the hood or room. We build to the specification provided; confirm the requirement with your project team before finalizing the design.
Will Labs USA handle my permit submittal or hazardous materials paperwork?
We can provide dimensions, drawings, and product specifications for your submittal package, but permit applications and hazardous materials disclosure documents are the owner’s or project engineer’s responsibility, since they depend on your facility’s actual chemical inventory and use.
Who removes and decontaminates the old fume hood?
Removal and decontamination of the existing hood are the owner’s responsibility, typically coordinated through EHS or a decontamination contractor, and need to happen before a removal crew takes the hood out. This is not something we perform as part of a hood supply order.
What if I need HVAC numbers before I have finalized every hood detail?
Send us the dimensions and chemical service list you have, even if some cabinet or accessory details are still being worked out. We can return hood-level CFM and dimensions your mechanical contractor needs to keep moving, and adjust finer details afterward.
Planning a Fume Hood Replacement?
Send photos, dimensions and your chemical list. A Labs USA specialist will review the old hood, flag what to change and quote the replacement.
Get a Free Quote Call (801) 855-8560