Acid Gas Ductless Fume Hood

What is the Acid Gas Ductless Fume Hood?

An acid gas ductless hood uses chemically impregnated carbon or alkaline media to neutralize acid vapours such as HCl, HF and SO2. It is used for small-scale acid handling where ducting is unavailable.

Overview

The hood uses an impregnated carbon or alumina-potassium permanganate media bed that chemisorbs acid gases, along with a prefilter. Airflow is 300–600 m3/h and face velocity 0.4–0.5 m/s. The body is polypropylene, resistant to acids, with a polypropylene or PVC work surface and sash. Media loading is 5–15 kg, with bed life dependent on acid concentration and quantity. Gas sensors for acid vapours such as HCl or NH3 can be fitted at the exhaust. Corrosion-resistant fans and fittings are used. Acid hoods should be limited to dilute or small quantities, since heated concentrated acids produce large vapour loads that can rapidly saturate the filter.

How does it work?

A ductless fume hood uses a fan to pull room air through the sash opening at 0.4–0.5 m/s across the work area, then through one or more filter stages before discharge back into the room. A prefilter removes dust, and activated carbon beds adsorb organic vapours through physical adsorption. Chemically impregnated carbon or specialist media can capture acids, ammonia or formaldehyde. A HEPA stage can be added for particles. Sensors or timers indicate filter saturation, and airflow monitors ensure correct face velocity. Because filters have finite capacity, the hood is limited to known chemicals in limited quantities, and filter selection must match the vapour. The body is typically polypropylene or epoxy-coated steel, with lighting and a control panel.

What are the key features?

• Impregnated carbon or alumina media bed
• Polypropylene body resistant to acids
• Corrosion-resistant fan and fittings
• Airflow 300–600 m3/h at 0.4–0.5 m/s
• Optional acid vapour gas sensors
• Media load 5–15 kg

What are the technical specifications?

A typical acid gas ductless fume hood configuration offers filter media of Impregnated carbon or alumina media, media mass of 5–15 kg, airflow of 300–600 m3/h, face velocity of 0.4–0.5 m/s, body material of Polypropylene and width of 600–1200 mm. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Acid Gas Ductless Fume Hood is used in dilute acid handling, electronics etching, teaching laboratories and sample digestion in small quantities. Across the wider Ductless Fume Hoods class, laboratories also deploy it for teaching laboratories, quality control and pharmacies.

Which standards and certifications apply?

Relevant standards and methods include ASHRAE 110 (testing performance of laboratory fume hoods), AFNOR NF X 15-211 (ductless fume cupboards), ISO 14644-1, EN 14175-1 (fume cupboards, vocabulary), GB/T 34269 and IEC 61010-1. Certification candidates for this model are CE and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Establish a chemical register before purchase and have the supplier confirm filter compatibility in writing. Change filters at the recommended interval or sooner if gas sensors or odour indicate breakthrough, because carbon saturation is sudden at the end of life. Test airflow and filter seals on installation and at least every 6–12 months, keeping records for audit. Place the hood away from doors and air currents, and with clearance to allow filter replacement. Dispose of used filters as hazardous waste. Train users to restrict quantities, keep sashes low and never use the hood for chemicals outside the compatibility list.

How do I select the right Acid Gas Ductless Fume Hood?

Choose an acid gas ductless hood for occasional dilute acid work where ducting is impractical. For heated or concentrated acid digestion, use a ducted hood with scrubber. RFQ: acids and concentrations, daily quantity, media type and monitoring.

How does it compare with other Ductless Fume Hoods variants?

Select by the chemicals used. Every application needs a chemical compatibility assessment from the supplier to match filter media, and the assessment should include quantities, frequency and breakthrough behaviour. Choose an activated carbon filter for organic solvents, impregnated carbon for acids or amines, and HEPA for particulates. Consider filter monitoring, such as gas sensors that signal breakthrough, rather than timers alone. Choose width, typically 600–1500 mm, noise level, and whether a base cabinet for storage is required. Ductless hoods are not suitable for unknown, high-volume or highly toxic chemicals, or for heated perchloric acid. Confirm local regulations on recirculating air, since some jurisdictions restrict their use.