HEPA HEPA HEPA
From "Health and Safety News," AIC News, January 2002

HEPA HEPA HEPA

For years the members of the Health and Safety committee have been whispering "HEPA." After September 11, we are shouting "HEPA" from the rooftops. With the potential for contaminated dusts from the World Trade Center disaster and other hazardous situations, the use of appropriate filtering systems on vacuum cleaners has become all the more important.

HEPA stands for High-Efficiency Particulate Air filter and refers to a material rated to trap 99.97% of airborne particles 0.3 microns and larger. The ULPA, Ultra-Low Penetration Air, filter traps even more, 99.99% of particles 0.12 microns and larger.

A HEPA vacuum is a 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 WTC 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), at least some 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 lookalike systems with names like hospital-grade HEPA, HEPA-like, or 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."

Some HEPA vacuums designed for home use eliminate the collection bag and use only "cyclonic" filtration to remove the dust before passing the exhaust through a HEPA filter. This type of system is fine for general housekeeping, but is inadequate for cleaning hazardous materials because of the very high risk of exposure when handling the uncontained collected dust.

The HEPA or ULPA filter itself is expensive so vacuums incorporate a number of pre-filtration stages to protect it. The collection bag is considered the first stage. The more intermediate filtration stages, the longer the HEPA filter will last.

A number of recent articles have referred to "HEPA filter bags." Even if true HEPA collection bags exist, which is doubtful, they would not be acceptable to use to clean up hazardous materials. Were the bag to rip, the contaminants would spew out of the vacuum creating an extremely hazardous environment.

Before using a HEPA vacuum, be sure to ask how to change the collection bag and maintain the intermediate filters and HEPA filter in a way that will not release contaminants. The act of opening the machine and removing the bag may create a dust cloud of exposure. Some manufacturers (Nilfisk, for example) have step-by-step instructions for changing bags and filters inside a glove bag (or a large, clear, garbage bag in a pinch). Others may want you to send the unit back to a service center. If you have access to local exhaust ventilation or a large lab hood, you may want to consider using this as your change area for smaller vacuum units.

The increased popularity of HEPA vacuums with allergy sufferers has resulted in an increase in the number of manufactures and models that are available. Prices and options vary widely. When comparing different vacuums, consider general durability, options like variable motor speed, the capacity of the tank/collection bag, the cost of replacement filters and bags, the noise level, and performance specifications like CFM, water lift, and the horsepower of the motor. A HEPA vacuum is always more expensive than a similar conventional vacuum. Prices range from extremely high to as little as $130.

A chart comparing a number of HEPA/ULPA vacuums, "A Heap O' HEPA Information" by Batyah Shtrum, was published in WAAC Newsletter in September 1997 (19/3). The article is available online at http://palimpsest.stanford.edu/waac/wn/wn19/wn19-3/wn19-306.html. Scroll down to get to the article.

—Chris Stavroudis, Paintings Conservator, Member of AIC Health & Safety Committee, 1272 N. Flores St., Los Angeles, CA 90069-2904; (323) 654–8748; cstavrou@ix.netcom.com