 |
 |
|
|
|
|
When chemicals are in use you need one of the following or a special hood:
Polyproplene Hoods for corrosive enviroments or metal free labs.
Polyproplene Hoods can be Vertical laminar Air flow, Conventional or By Pass-hood.
Demanding Environments where polyproplene is often specified is Trace Metal Analysis, Marine Science, Material Science, Soil Science, Semiconductor, Toxicology, Environmental Toxic Analysis, electrical Engineering, Metallurgy, Chemcial Engineering, Water Treatment labs.
EXAMPLES OF HOODS WITH SPECIAL FEATURES:
Hoods usually have conventional rising glass sash, but can have combination sliding and rising or a hinged sash.
Special accessories for special hood applications and for energy savings:
Acid Digestion Hoods are usually a polypropylene hoods with polypropylene cabinets, counter, and polypropylene ducting, and a polypropylene fan. This provides the best value for the money for long life when acids are the only work being done or the enviroment is corrosive.
You may need a safety station.
Did you know the chemotherapy drugs should be mixed in a safety station to avoid techincal staff exposure?
The answers tells you what type of hood you need.
What about air quality (exhaust)issues?
Contact us with your requirements, we can help.
Dilution was said to be the solution to pollution. (It is not.)
Some companies are capturing and containing and appropriate disposing of filtered waste.
When selecting a hood, let us help you define what you expect, the purpose and best practice.
Many states provide credits or insentives for pollution reduction equipment.
As you answer basic questions, the selecting process begins:
If you need to protect yourself from dust, chemicals or fumes:
A chemical hood is what you need and a By-pass or similar hood will do the job.
If you have harmless odors or heat only, you can use a canopy hood.
If you need to protect both, product and yourself, you need safety cabinets, with laminar flow.
Determine minimum width, height, depth requirement within hood.
What equipment or apparatus will you put in the hood?
What special electrical or other services will you require.
A list of chemicals, hazards, and possible future uses for hood.
This chemical list help with selection of liner material, appropriate work surface, and fan.
The approximate quantities stored helps with selection of hood base or transport cart and other storage or venting issues.
Develope a past problem list, this can help with selection.
Sash options and style as well as other considerations.
You may need a special lexan sash or other modifications to eliminate problems in the future.
By-Pass Chemical Hood * * * Canopy Hood * * * Cone or Instrument Vent (IVT)
PARTS OF A Hood ACCESSORIES
Fume Hood Accessories Common:
Fume Hood Fans have accessories and optional special coatings on Steel
Properly sizing of the fan or blower is key to proper hood function. Contact us to help in selecting a hood, fan or for brochures or prices.
Remember ask yourself do you need to protect personnel, product, or both?
Scrubbers and filter units now provide a better option, for air quality, call for information.
Adding a scrubber or filtration can reduce pollution and have economic benefits.
Remember to use your browser Back or Arrow to close pictures you enlarge:
What work space in the hood will you require?
Use your back or browser arrow to close any pictures you enlarge.
First is a Canopy with fan before the closure panel conceals the fan.
Next is a canopy hood capturing odor at the source also pictured a conventional hood.
The conventional hood has a combination sash sliding and rising.
The Blue and white By-Pass is a small 3 foot hood with air-foil, sash pocket, remote control fixtures, and a special open to the floor base cabinet which is also ADA compliant when both doors are open.
OTHER SPECIAL FUME HOODS TYPE or Style:
Learn more about health risks of nanomaterials at
www.cdc.gov/niosh/topics nanotech/background.html
Remote controlled fixtures, alarms, slabs to improve air flow, side shelf units, and
lattice or monkey bars, remote control fixtures can be deck mounted or panel, sinks, steam baths, and special electrical components if outside on face of hood or in isolated compartment of the base cabinet can be
Specials to accommodate special equipment.
Many unique accessories:
Accessories including: steam table, trough, light, worktop, steam cone
Alarms & Monitors, Electrical Outlets
Fixture can be mounted in Fume Hood Base Cabinets, but need to be isolated from base cabinet content.
Fume base cabinets can be cut into for sinks, but only if not used for chemical storage.
Acid bases used as fume hood base cabinets can have sinks in them, but should not have any metal tailpieces or piping and should be sealed except for optional venting.
We have vent kits. Venting of bases into hoods is better than no venting; but is still not an excellent practice.
Venting to outdoors is the first choice and best practice if venting is going to be needed.
Venting of flammable cabinets should be to outdoors.
Flammable cabinets should not be vented, as that defeats purpose of self-closing fuse-link doors.
Special Fans of PVC and Fiberglass are available
Fans can be Explosion Proof, most should be spark resistant.
Fan accessories include covers, vibration pads, stacks, elbows, Wyes, dampers (not recommended for fume hoods).
Hood ducting is steel (316 SST preferred, if metal is an acceptable material.
Ducting of PVC or fire rated fiberglass is preferred for fume hoods.
Galvineal and coated steel ducting is sometimes acceptable.
We can help with fan selection and hood selection.
Note fans must be sized to the hoods, canopy hoods or IVT, and the size of the duct size, length of the duct run is needed to calulate fan required.
Fans must be appropriate to the work being done in the hood, we can help.
Do not gang together hoods, as mixed chemistry in the duct can lead to unexpected consequences.
**Fume Hood Fans have accessories and many options and optional special coatings on Steel Fans
Special Fans are PVC or Fiberglass
Sizing Fan for the Hood
Fume hood Fans (blowers) needs a stack that is recommended 8 foot above roof.
PS: VAV is not for most. VAV and Low-flow was devised as a means to reduce energy costs in
"fume-hood-heavy educational facilities. One to three hoods does not usually consider VAV or
low-flow hood. Low flow may go the way of the add-air, the disadvantages which are discussed
in a technical report at ashrae.org. Goal of VAV to reduce annual operating costs, stating
that added cost of the hood is made up for by energy savings, if flow monitoring accuracy
and accurate hood alarms, sophisticated air-conditioning and heating controls are in place,
and sophisticated staff is available as well as the willingness to contract for building
control maintenance. Running low-flow or VAV at common operating velocities of 60 fpm is not
safe based on the way most users work in hoods. The hood is a piece of safety equipment,
and trying to save annual cost is important, but is it worth the work liability and risk?
All low-flow or VAV hoods create more time for contaminants to roll around inside the hood before
they exit, leading to buildup in the hoods. Equipment and fixtures in the hood will show the
the results in shorter life. The design of VAV has improved; however cross-drafts and
operator movement is an influence. Some states and cities have regulations not allowing low
flow or VAV hoods. Rather than spending resources to change code or regulations manufacturers
and users need to remember look at the hood as a piece of safety equipment, not HVAC products.
Like other reasearcher vs. administration preferences low-flow or VAV hoods like the "open-lab
plan" leaves a lot to consider. Satisfactory performance under all situations is important with
safety equipment. Limiting size and higher or low air-flow is an impact on performance, creating new
computer controlled sash and air-handling may not perform when challenged with day to day work
and various situational changes. Just as filtered hoods can not handle all of the demands of
most chemical hoods needs, the VAV is more costly and may not be the hood for your situation.
Remember a hood is a piece of safety equipment first, not part of a ventilation system.
PS. Fume Hood exhausting dialogues starting as more effort is being made to contain and capture rather than just diluting exhaust. More hood users are asking,
what harm is there in what is exhausting to the outdoor? If our children play outside and the wind blows exhausted fume hood air in their direction, we are concerned.
It was said for years, the solution to pollution is dilution, now that may have been delusion. Diluted or concentrated chemical exposure is part of current chemical exposure limits language. We describe a situation for potential for evaporation; as potential concentration of chemical. There is the accummulation; there by mixed chemistry potentials, it would have been better if all previous science and technology had not relied so on dilution.
Solutions are only discovered when there is an understanding of or an expressed problem. Current technologies and more knownlege with new ability to monitor, measure in terms of ppm, and databases helps us understand impacts of some chemicals. In the future, we will make more informed decisions on what is acceptable practices.
Exhausting chemical hoods will soon be given more attention. Filtering is not necessary in all situations.
No regulatory mandates filtering or scrubbing, but that is coming as there are more acceptable ways to deal with fume hood exhaust and as commercial and industrials scrub and mitigate pollution all others will be soon required to do the same. When making the decision to purchase a hood, remember
to review established TLVs for health and safety within the lab, again this is where your list of chemicals is needed. I have a book and often look up Total Limit Values, or you can contact (ACGH) American Conference of Government Industrial Hygienists, Cincinnati, Ohio, to purchase one.
The best responsible practice may be to include a scrubber or get a filter system with the hood, or plan to add one. Some states provide tax incentives for pollution control equipment. Recirculate and cleaning, then exhausting is going to become
more and more important. Ignorance is no excuse, like so many things limiting ones liability is critical and wise.
The real solution to pollution is to find ways to not create or to turn exhausted or byproducts into a more useful substances as industry is beginning
to do or contained and dispose of captured pollutants appropriately.
Parts of a Hood
Stack for fans