Acid Digestion and Perchloric Acid Fume Hoods
Hot mineral acids, hydrofluoric acid and heated perchloric acid each need a different hood. Learn how acid digestion hoods, perchloric wash-down hoods and scrubbers differ, then send us your acid list for a recommendation.
Fume Hoods for Acid Digestion and Corrosive Fumes
Acid work is where the wrong fume hood costs the most. Hot mineral acids attack standard liners, glass sashes and ductwork, and heated perchloric acid can leave explosive residue in the exhaust system. A general-purpose chemistry hood that works well for solvents can corrode in a few years of daily nitric or hydrochloric digestions.
The right place to start is your acids and how you heat them. That one answer decides whether you need a ducted hood, which liner and sash material fits, and whether you also need a wash-down system or a scrubber. This page explains each choice in plain terms so you can have a better conversation with your EHS officer, your mechanical engineer and us.
Ducted
Plan on it for heated acid work
PVC / PP
Common acid digestion liners
316 SS
Common perchloric liner
Separate
Scrubbers usually quoted as a line item
If you are still comparing general hood types, start with the laboratory fume hood hub, which includes a process-by-process selection table and a quote checklist. This page goes deeper on the acid-specific rows of that table.
Ducted or Ductless for Acids?
For acid digestion and other heated acid work, plan on a ducted hood that exhausts to the outdoors. Here is why.
Why ductless is usually the wrong fit
- Filters return air to the room. A ductless hood cleans air through filters and recirculates it. Manufacturers limit these hoods to approved chemicals in limited quantities, usually with little or no heating. One major hood manufacturer specifically says no extreme heating, such as acid digestion, should be done in a ductless hood.
- Acid filters have a fixed capacity. Acid-specific carbon filters exist, but a hot digestion can load them quickly. Some ductless saturation sensors are designed for organic vapors and do not detect mineral acid gases such as HCl, nitric or sulfuric acid.
- Perchloric acid is not permitted in ductless hoods.
SEFA 9-2026, the industry recommended practice for ductless enclosures, limits them to applications the manufacturer has approved and calls for the highest filtration category, with continuous saturation monitoring, on ductless fume hoods.
Where ductless can still work
Room-temperature acid transfers or small-volume titrations can sometimes run in a ductless hood with acid-rated filters, after the manufacturer reviews your chemical list and your safety officer approves it. See ductless fume hoods for what they do well.
Acid Digestion Hoods
An acid digestion hood is a ducted hood built to handle hot, concentrated mineral acids such as nitric and hydrochloric acid, and in many designs hydrofluoric acid. It looks like a standard bench-top hood from the front, but the materials that touch the fumes are different.
- Plastic interior. A polypropylene or unplasticized PVC liner and work surface that resist acid attack where powder-coated steel or fiberglass would degrade.
- Polycarbonate sash where hydrofluoric acid is used, because HF etches glass.
- Corrosion-resistant fittings, exhaust collar and ductwork so the parts you cannot see last as long as the liner.
- A heat check. Plastic liners have temperature limits. For example, Labconco rates its Protector PVC liner for continuous use up to 140 °F (60 °C), and its PVC acid digestion model is intended for mineral acids that do not involve high temperatures. Tell us the surface temperature of your hot plate or digestion block so the liner matches your heat load.
A standard acid digestion hood is not a perchloric acid hood. Manufacturers state that their acid digestion models are not for perchloric work.
Most acid digestion hoods are configured to order around your width, sash type, services and base cabinets. Pair the hood with an acid and corrosive storage cabinet underneath, and choose service fixtures rated for the environment from the fume hood accessories page.
Perchloric Acid Hoods
When perchloric acid is heated, its vapor can condense inside the hood and duct and form perchlorate salts that are shock-sensitive. That is why NFPA 45 limits heated perchloric acid work to hoods specifically designed for it and labeled for perchloric acid operations. The exception is when vapors are trapped and scrubbed before they are released into the hood.
What a perchloric hood system usually includes
- A seamless stainless steel or PVC interior with an integral work surface and a rear drain trough
- A water wash-down system that sprays behind the baffle and through the exhaust duct
- A dedicated exhaust duct that runs as short and straight as possible, is not tied into other exhaust, and drains back toward the hood
- An acid-resistant, spark-resistant exhaust fan with the motor outside the airstream
- Acid-resistant, nonreactive gaskets and sealants, and no organic materials or solvents in the hood
A perchloric hood is used only for perchloric work, and it is washed down on a schedule your EHS officer sets. The ANSI/ASSP Z9.5 laboratory ventilation standard calls for routine wash-down while the hood is in use, and says perchloric hoods should not be manifolded with other hoods unless a scrubber sits between them.
Stainless steel versions such as the Labconco Protector Stainless Steel Perchloric hood use a seamless Type 316 stainless liner with an integral work surface, drainage trough and built-in wash-down, and are offered in several widths. Some accessories, such as duct wash rings, are ordered separately, so confirm exactly what is included on your quote.
Some labs avoid a full perchloric system by trapping and scrubbing the vapor right at the digestion apparatus. Whether that is acceptable is a decision for your safety officer and the authority having jurisdiction.
Do Scrubbers Come With the Hood?
Usually not. A scrubber is generally a separate component, and there are two kinds:
Whether you need either type depends on your acids, volumes, building exhaust and local air-quality rules. On your quote we list any scrubber, wash-down accessories and exhaust fan as separate line items so you can see exactly what is included, and we can coordinate with your mechanical contractor on the duct, fan and water connections. For duct routing basics, see fume hood ductwork and exhaust design.
Liner and Work Surface Materials at a Glance
| Material | Typical use | Watch for |
|---|---|---|
| Polypropylene | Strong mineral acids, acid digestion, hydrofluoric acid | Heat limits; not for perchloric unless the manufacturer rates it |
| Unplasticized PVC | Mineral acids at moderate temperatures; some perchloric designs | Continuous temperature rating (often about 140 °F) |
| Type 316 stainless steel | Perchloric acid hoods; high-heat work | Not ideal for hydrochloric or hydrofluoric acid |
| Fiberglass (FRP) | General chemistry with moderate acid use | Not a dedicated acid digestion or perchloric liner |
| Epoxy or phenolic resin tops | General chemistry work surfaces | Check each acid and temperature against the resistance chart |
Liner choices for the whole Labs USA hood line are summarized on the fume hood accessories page. For work surfaces outside the hood, compare laboratory work surfaces.
What to Have Ready Before You Request a Quote
- Every acid, with its concentration and the largest volume open at one time
- How you heat it (hot plate, digestion block, microwave digester) and the maximum temperature
- How often and how long you run digestions
- Whether perchloric acid or HF is used now or may be used later
- Available exhaust: a path to the roof, an existing fan, or a new dedicated duct
- Storage needed below the hood, such as a vented acid/corrosive cabinet
- Your EHS contact and any local code or air-quality requirements you already know about
Send your acid list
Chemicals, concentrations, heat source and frequency.
We recommend a hood
Hood type, liner, sash and base cabinet that fit the process.
Coordinate exhaust
Duct, fan, wash-down and any scrubber, with your mechanical contractor.
Final sign-off
Your EHS officer and code official confirm the design.
Who decides the final design?
Your EHS officer, mechanical engineer and local code official. We help you pick hardware that fits their requirements; containment is commonly verified with the ANSI/ASHRAE 110 test method after installation. You can also sketch a general-purpose hood in the Fume Hood Configurator.
Shop Acid Storage Cabinets Online
Store acids safely next to your digestion hood. These blue acid/corrosive cabinets can be ordered online; acid digestion and perchloric hoods themselves are configured to order, so request a quote for the hood.
Acid and Perchloric Fume Hood FAQ
Can a ductless fume hood handle acid digestion?
Is an acid digestion hood safe for perchloric acid?
Do acid fume hoods come with a scrubber?
Are acid and perchloric hoods in stock?
Which liner should I choose for hydrofluoric acid?
Who decides the final design?
Get a Recommendation for Your Acid Process
Send us your acid list and digestion setup, and we will recommend a hood, liner and exhaust approach.