May 2002 Volume 22 Number 2
May 2002 Volume 22 Number 2
I am surprised and a bit disappointed at how few colleagues have HEPA vacuums in their studios. Every year there are more stories about hidden sources of contamination in the artworks we treat, more stories of adverse reactions to mold, and the occasional story of someone working with historic materials developing health problems.
One of the simplest things we can do, beyond not ignoring our own common sense, is to invest in and use a HEPA (or ULPA) vacuum. Good studio hygiene goes a long way to minimizing exposure to known, and particularly unknown, hazardous materials. And one of the key aspects of good studio hygiene is the routine use of a HEPA filtered vacuum. Recent work by Monona Rossol (ACTS) indicates that anyone working with pastels, artists included, should have (and use) a HEPA vacuum for clean-up. (This caution would also apply to the use of dry pigments).
On the following pages you will find a new and completely updated chart on HEPA and ULPA vacuums. I hope that this information will remove that last obstacle to your getting a HEPA vacuum of your very own. Too expensive you say? Bollocks! That excuse just won’t fly any more.
Are you too worried about how to deal with safely changing the filter bag, how often to replace the HEPA cartridge, or how to dispose of the sucked-up filth? Relax, get over it. Compared to the occasional sweeping with a broom, using a DustBuster, or even a mop and pail of water, your exposure is much lower and the environmental / legal consequences are no worse if you switch to using a HEPA vacuum. Just because you’ve vacuumed the floor with a HEPA, the crud in the filter bag is not instantly toxic waste, and it is certainly not any more toxic that when you swept it up with a dust pan.
That’s not to say any of us should be laissez-faire about cleaning up truly contaminated materials – lead, asbestos, arsenic, and various and sundry biological hazards. Then you do have to worry about changing the filter bag in a way that doesn’t contaminate you or your workspace, and know that the contents are indeed hazardous waste and must be disposed of accordingly.
If your work does involve occasional serious hazardous exposure, perhaps you should consider getting two HEPA vacuums — one for general studio clean-up and one for the hazardous stuff. Get a Nilfisk for vacuuming the arsenic laced animal specimens and a Eureka Mighty Mite HEPA for vacuuming the floor and cleaning the reverse of paintings.
The accompanying chart contains almost everything you need to know about your HEPA/ULPA options. The rest is explained here.
Let’s start with the basics. The HEPA filter (High Efficiency Particulate Air filter) retains a minimum of 99.97% of particles down to and including 0.3 microns (µ) in diameter. ULPA filtration (Ultra Low Penetration Air filtration) retains 99.999% of particles down to and including 0.12µ. HEPA or ULPA filtration is added to a vacuum to trap the very fine particles that can pass through a conventional filter bag and be pumped through the vacuum and into our breathing space.
A HEPA vacuum is any vacuum cleaner designed with a HEPA filter as the last filtration stage. HEPA is the legal standard for lead abatement and asbestos mitigation. (ULPA is legal, too.) For those tasks as well as cleaning up World Trade Center dust, HEPA filtration or better is required.
An ULPA filtered machine provides better capture for extremely fine particulates. Examples of such materials include powdered organic dyes, condensed lead fumes (around molten lead or leaded bronze), viruses, or very finely divided modern pigments like the cadmiums.
When selecting a vacuum, make sure you get true HEPA or genuine HEPA filtration. Avoid lesser grade look-alike systems with names like hospital-grade HEPA, HEPA-like, Micron, or those fitted with Gore-Tex microfilters. These are cheaper but in spite of similar looking ratings, they are not acceptable for conservation work. It is also important that the vacuum be designed and constructed so that all the air taken in is passed through the HEPA filter before it is exhausted. This is sometimes referred to as a HEPA sealed system. The filtration can take place before the motor or after and there are advantages and potential disadvantages to each configuration.
In the chart, I’ve only considered canister vacuums. Uprights are an option, but seem ill suited to general conservation work. Some HEPA vacuums, particularly uprights, eliminate the filter bag and use only “cyclonic” filtration to remove the dust before passing the exhaust through a HEPA filter. This type of system is fine, I suppose, for general housekeeping, but is inadequate for cleaning potentially hazardous materials because of the very high risk of exposure when disposing of the collected dust.
The HEPA or ULPA filter itself is expensive so vacuumsincorporate a number of pre-filtration stages to protect it. The filter bag is considered the first stage. The more intermediate filtration stages, the longer the HEPA filter should last.
Most manufacturers give suggestions on how often the HEPA or ULPA and prefilters need to be changed. But, it’s nothing to obsess over. If the filters are clogged, the vacuuming efficiency is reduced, but you are not releasing anything bad into the air. You may not be picking up that hazardous crumb, but you are certainly not releasing it either.
The table lists as much relevant information as I could find on each vacuum. There are numerous other options which are not related directly to the vacuum’s efficiency. Most manufacturers offer many options for power heads which are important for cleaning your home (and why not get a HEPA vacuum for home?) but not particularly relevant for conservation use.The chart lists three parameters which help you evaluate the cleaning power of the vacuum. The cfm number is the cubic feet of air per minute drawn in through the hose. Water lift is a gauge of the suction strength and is the number of inches of water the vacuum could draw straight up into the air. (For reference, 33 feet of water is one atmosphere or 15 psi).
The two values measure different components of the vacuum’s efficiency – how much air it “sucks” and how strongly it pulls that air. The two numbers taken together give a very good idea of how well the vacuum cleans.
The motor horsepower (often converted from the suction motor’s wattage or amperage values) gives an indication of how strong the suction should be. With equally well designed suction motor and fan design, a higher horsepower value should have better dirt pick up. However a higher horsepower motor with lower cfm and water lift values simply indicates an inefficient design.
In conservation, however, we often want to reduce the vacuum’s suction. Conventionally, this is done with an air bleed in the handle or wand of the vacuum, and all vacuums still offer this control option. Many vacuums also offer motor speed control, either standard or as an option.
Any vacuum can be connected to a Variac, motor speed controller, or light dimmer and run at reduced power. However, using a device not designed by the manufacturer is done at your own risk. Most vacuums rely on the air flow passing through the filter for cooling. If the airflow is reduced, particularly if the device you are using too slow the motor also increases the heat it generates, you may overheat the motor and cause serious damage to the vacuum. (This being said, I’ve also seen vacuums run for hours and hours and hours slowed with a conventional light dimmer switch). Certainly, were the manufacturer to find out you were using an unauthorized variable speed controller on the vacuum, your warrantee would be voided.
The capacity of the vacuum is given in the tank size value. Sometimes the number listed is the capacity of the filter bag which is actually slightly lower than the tank size. The larger the tank size, the less often you should have to change filter bags.
Anyone who has spent time working with a noisy shop-vac will understand the value of a quiet vacuum. This can be gauged by the noise level number – higher is louder. When given, I’ve indicated the distance from the vacuum the noise level was measured.
A few of the listed vacuums are wet/dry. When used dry, they can be fitted with a conventional filter bag. In this case, wet refers to water and not solvents. None of the listed vacuums are explosion proof. If you’ve got heaps of money and vacuuming solvents or solvent fumes is a concern, the Nilfisk SS Vapor Vac looks very interesting, but do note the price of the replacement activated charcoal filter bed.
The vacuums are also coded for their intended use: H for home use, S for shop, and I for industrial. That information along with the weight, dimensions and construction give you a pretty good sense of what you are getting for your money.
The price of each unit is given, either as the manufacturer’s suggested retail or as a street price, the lowest price I came across while researching this article. I’ve also listed the cost of filter bags and replacement filter units.
Finally, information on the manufacturer and various suppliers are given. While not exhaustive and strongly US west-coast biased, it certainly is a start in finding someone to give your money to. Many of the distributors offer their products via the internet as well as conventional retail outlets.
One thing I was not able to note in the chart, but a feature I really like, is whether or not the filter bag has a provision for sealing the used bag. This makes so much sense – when you change the dirty filter bag, you simply close a little door or slider and keep the filth inside from pouring out.
So, what do I recommend? First, consider your needs and whether you need variable speed control. If you need it, you are looking at the higher priced units. I would stay away from power head options and get just a unit with a simple floor nozzle. This avoids having power running through or along the hose.
If you use shop tools, the Fein 9-55-13HEPA has a neat feature – you can plug your hand power tool into an outlet on the vacuum. When the tool is switched on, the vacuum springs to life.
HEPA or ULPA? If it weren’t my money, I would go for ULPA. My own vacuum is a HEPA, but when I eventually replace the filter, I might spring for an ULPA.
If money is an issue, whether it’s your money or not, I would consider the Eureka Mighty Mite HEPA or the Sanitaire S3686 (which seems to be the same but has better quality wands and tools). I’ve not used one, but I’ve kicked the tires and slammed the HEPA filter door and was impressed. Because the Mighty Mite HEPA has only 3 filter stages, I would only use it with Eureka’s Filteraire line of filter bags which offer better filtration at a slightly higher price.
Now, you are a HEPA vacuum expert. Go out, spread the word. Buy!
Chris Stavroudis is a conservator in private practice.Special thanks to Mary Piper Hough who assisted with the research for this article and Batyah Shtrum who prepared the original A Heap 'o HEPA Information Technical Exchange submission which apeared in the September 1997 WAAC Newsletter
The following are the manufacturers /suppliers of the HEPA vacuums listed in the chart on pp. 14 and 15.
See Comparison of HEPA/ULPA Vacuums (PDF)
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