Polypropylene Acid Digestion Hood

What is the Polypropylene Acid Digestion Hood?

A polypropylene acid digestion hood uses welded PP body, liner and sash to resist nitric, hydrochloric, sulfuric and hydrofluoric acid vapours. It is the standard choice for open-vessel trace-metal digestions with corrosive acids.

Overview

The hood is fabricated from 8–12 mm welded polypropylene, giving a seamless, acid-resistant interior with no metal fasteners exposed to vapour. The work surface is PP or ceramic, with a spill lip and a sink or drainage point. Internal height of 900–1200 mm accommodates hotplates, digestion blocks and reflux glassware. Face velocity is 0.4–0.6 m/s, and a PVC or polypropylene centrifugal fan moves 500–1500 m3/h to a corrosion-resistant duct. A polycarbonate or PP sash protects the operator while allowing access, and a washdown spray can be fitted to rinse the rear baffle. Interior lighting, a service panel and airflow monitoring complete the design. The all-plastic construction is also suitable for hydrofluoric acid work, where glass and most metals would be attacked.

How does it work?

An acid digestion hood encloses the hotplate or block digester on a chemically resistant work surface and draws acid vapours away through a rear baffle and exhaust duct. The body, liner and sash are made from polypropylene, PVC or acid-resistant stainless steel so that nitric, hydrochloric and hydrofluoric acid vapours do not corrode the surfaces. Face velocity at the sash is held at 0.4–0.6 m/s, and a corrosion-resistant fan, usually plastic or PVC-coated, moves air to atmosphere. Because digestion releases dense acid fumes and heat, larger air volumes and deeper baffles are used than in a general-purpose hood. Some models add a scrubber that neutralises acid in a packed column before discharge, reducing emissions to the stack. Water washdown and low dead volume help prevent salt accumulation and cross contamination between trace-metal samples.

What are the key features?

• Welded polypropylene body, liner and sash
• 8–12 mm PP panels, no exposed metal fasteners
• Internal height 900–1200 mm for digesters
• PVC or PP corrosion-resistant centrifugal fan
• Washdown spray for rear baffle
• Face velocity 0.4–0.6 m/s with airflow monitor

What are the technical specifications?

A typical polypropylene acid digestion hood configuration offers body material of Welded polypropylene, 8–12 mm, work surface of PP or ceramic with spill lip, internal height of 900–1200 mm, width of 1200–1800 mm, face velocity of 0.4–0.6 m/s and airflow of 500–1500 m3/h. 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 Polypropylene Acid Digestion Hood is used in trace-metal digestion with HF, environmental sample prep, food elemental analysis and geological assay. Across the wider Acid Digestion Hoods class, laboratories also deploy it for trace-metal sample digestion, environmental soil and water analysis and food and feed elemental analysis.

Which standards and certifications apply?

Relevant standards and methods include EN 14175-2 (fume cupboards, safety and performance), EN 14175-3 (type test methods), ASHRAE 110 (method of testing performance of laboratory fume hoods), GB/T 34269, ASTM D1193 (reagent water used in digestion blanks) 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.

Install the hood away from doors and air supply diffusers, and provide corrosion-resistant ducting with the correct slope and drainage. Commission face velocity and, where required, containment by tracer gas at the sash. Establish a hotplate and acid-usage log, and inspect the liner, sash and fittings monthly for etching or discoloration. Replace exhausted scrubber media on the schedule set by the acid load, and treat scrubber effluent as acidic waste. Keep the work surface clean and free of salt deposits, especially around the inside of the duct connection. Provide secondary containment trays and confirm the fan, duct and roof discharge are rated for the acids in use.

How do I select the right Polypropylene Acid Digestion Hood?

Choose polypropylene when hydrofluoric, nitric or hydrochloric acid is used and metal contamination must be avoided. Confirm internal height for reflux glassware and specify the washdown option for HF work. RFQ: acids and concentrations, vessel sizes, daily throughput and duct material.

How does it compare with other Acid Digestion Hoods variants?

Choose the construction from the acids used. Hydrofluoric acid attacks glass and requires polypropylene or special liners; nitric and hydrochloric acid work needs polypropylene, PVC or acid-grade stainless steel. Decide whether a scrubber is required by local emission limits and the acid volumes handled. Match the internal height to the hotplate, rack and reflux glassware, and choose depth for tall condensers. Consider a dedicated water washdown system if the duct could collect salts. Select face velocity monitoring and alarms, and a work surface with a spill lip. Confirm the fan is corrosion-resistant rather than mild steel, and plan for acid-resistant duct material and drainage. Large multi-position digestions may need a walk-in or dual-duct layout.