Safe Laboratory Furniture Equipment Steel Chemical Fume Hood

Basic Info.

Packaging & Delivery

Product Description

When fume hoods are "on" and operating, air is pulled through them via a blower, creating a negatively pressurized environment to protect the user from harmful vapors. The air travels at a certain speed or velocity. The velocity of a fume hood is measured in the plane of the sash, and referred to as the face velocity, measured in feet per minute (fpm). This term is very important since standards reference face velocities at which fume hoods may be operated.

The face velocity is related to the amont of air being pulled through the fume hood, or the volumetric rate. This number is typically measured in cubic feet per minute (CFM). The more air that is pulled through a fume hood's openings, the faster the air will travel.

Most of us can relate this to our experience of using a garden hose to water the lawn. If an area is out of range of the garden hose, you can place your thumb over the opening of the hose to make the water spray farther. When you block a portion of the opening, you speed up the water's velocity, though the volume of water being pumped through the hose remains the same.

Since water and air are considered fluids, the same physics apply to both. The face velocity (fpm) is dependent upon both the amount of air going through the hood (CFM) and the size of the opening the air passes through.

Acid digestion

These units are typically constructed of polypropylene to resist the corrosive effects of acids at high concentrations. If hydrofluoric acid is being used in the hood, the hood's transparent sash should be constructed of polycarbonate which resists etching better than glass. Hood ductwork should be lined with polypropylene or coated with PTFE (Teflon).

Downflow

Downflow fume hoods, also called downflow work stations, are typically ductless fume hoods designed to protect the user and the environment from hazardous vapors generated on the work surface. A downward air flow is generated and hazardous vapors are collected through slits in the work surface.

Perchloric acid

These units feature a waterwash system (scrubber - see below) in the ductwork. Because dense perchloric acid fumes settle and form explosive crystals, it is vital that the ductwork be cleaned internally with a series of sprays.

Radioisotope

This fume hood is made with a coved stainless steel liner and coved integral stainless steel countertop that is reinforced to handle the weight of lead bricks or blocks.

Scrubber

This type of fume hood absorbs the fumes through a chamber filled with plastic shapes, which are doused with a scrubbing medium. The chemicals are washed into a sump, which is often filled with a neutralizing liquid. The fumes are then dispersed, or disposed of, in the conventional manner.

Waterwash

These fume hoods have an internal wash system that cleans the interior of the unit, to prevent a build-up of dangerous chemicals.

Fume Hoods vs. Biosafety Cabinets

Both chemical fume hoods and biosafety cabinets are specialized types of laboratory equipment. While chemical fume hoods and biosafety cabinets look similar and both protect laboratory workers from laboratory hazards - their purpose, function, and operation differ significantly.

A chemical fume hood is designed to remove chemical fumes and aerosols from the work area while a biosafety cabinet is designed to provide both a clean work environment and protection for employees who create aerosols when working with infectious agents or toxins.

The images below show basic examples of the airflow design for the two types of cabinets.