Working in A Vacuum

Particles in, particles out. A vacuum cleaner that pulls in the most particles and releases the fewest back into the environment, and is easy, safe and healthy to use, is the right choice. Choosing a vacuum for an educational facility should be that simple.

In light of such clear criteria, why do so many vacuum cleaners come with bells and whistles, sales demos and tricks, colors, designs and marketing schemes? The answer also is simple. Intense competition forces vacuum-cleaner makers to play a game of promotional one-upmanship.

“You have 12 amps? I have 14. You have micro-filters? I have HEPA. You have three-level filtration? I have five. Your model is fluorescent blue? Mine is iridescent burgundy. Your vacuum is $299? Mine has all that plus lifts bowling balls for $249.”

That makes it hard for manufacturers, facility-service providers and purchasing agents to tell or discern the truth and make wise choices based on correct information.

Debunking myths

What's the key to making a wise vacuum cleaner purchase? Knowledge and education. Several myths about vacuum cleaners do not stand up to scrutiny:

Myth No. 1: Amps mean performance. Amps are a measure of electrical current, not vacuuming performance. Measuring a vacuum cleaner's performance based on amps is like buying a car based on how much gas it guzzles. The design of the entire machine and how it handles and controls airflow and incorporates filtration determines its quality, not the electrical energy it consumes.
Myth No. 2: Everyone needs HEPA. The school environment needs to have the fewest particles released or driven into the air — regardless of whether that vacuum is HEPA or not. Some micro-filtered systems accomplish this just as well as some systems labeled HEPA. Find out what the “particles out” are to derive the all-important information.

Keep in mind that even high-end HEPA-filtered vacuums still may be driving dust airborne because of the impact of a beater brush against the carpet. With uprights or canisters equipped with power heads, the critical information to acquire is how much airflow and lift are occurring at the beater brush/floor interface. This will help determine whether particles are being pulled into the vacuum or driven airborne. The extra-wide orifice on some upright vacuums and power nozzles results in greatly diminished suction at the tool head and poor soil capture.
Myth No. 3: Picking up a “bowling ball” shows cleaning power. The bowling ball trick is just that — a trick. This sales technique is based on the power of a suction cup. Have you ever stuck a suction cup on a mirror and tried to remove it by pulling directly away from the mirror? It's hard to do. Why? Once a seal is created on a smooth surface, the seal is difficult to break. Does a vacuum tool's ability to form a seal around a bowling ball and pick it up like a suction cup have anything to do with how well the vacuum can remove soil from a surface? No.
Myth No. 4: All vacuum bags are the same. Multi-ply micro-filters provide better vacuum efficiency than generic single-ply paper filters. Micro-filter bags have greater media density and thus capture far more fine dust. One-ply generic bags have relatively large pores that allow fine dust to escape, lowering indoor air quality, and increasing health risks and the need for dusting.

Also, filter bag size does matter. The greater the “area” of the filter media, the longer airflow, suction and cleaning can be sustained. For this reason, at least one major manufacturer of vacuum cleaners promotes its filters by measuring and publishing the total area — in square inches or centimeters — of its filter bag media.
Myth No. 5: All vacuum belts are the same. Not all vacuum belts are created equal. A cheap vacuum belt will stretch, slip and wear out quickly, whereas a high-quality belt is geared or sprocketed like an automobile timing belt and can last for years. In addition, geared or sprocketed belts do not slip, ensuring better and more consistent soil pickup and removal. Sprocketed belts help ensure better overall performance, and enable the staff to spend more time cleaning and less time changing belts.
Myth No. 6: Cyclonic systems do not use filters and require less maintenance. Virtually all cyclonic or bagless vacuuming systems use a final filter to catch the dust that cyclonic filtration cannot remove from the airflow. This often is a HEPA media filter. This final filter will require regular cleaning or replacement to ensure optimal performance. If a customer fails to perform needed filter maintenance, a vacuum will not perform as intended. The cost of replacing the final filter may equal or exceed the cost of using conventional bag filter media. The quality of cyclonic systems varies widely. Request the all-important “particles in, particles out” information in the form of test data from the manufacturer to determine overall performance.

Some vacuum cleaners actually are designed to produce cyclonic airflow, even with conventional micro-filters. Ribbed panels in the filter-containment area create a rotating column of air inside the filter bag so soil is deposited evenly on the sidewalls of the filter where it has the greatest surface area, ensuring sustained airflow longer.
Myth No. 7: All vacuum cleaners have similar design features and are equally easy to use. Ergonomic design, weight and other factors affecting ease of use vary widely. Handle weight is a critical factor with uprights, as is ease of rolling and maneuverability. Canister vacuums vary widely in shape and design. One model balances the weight primarily over the large rear wheels to facilitate nimble handling and ease of pulling. Some canisters trip over power cords, while others roll over such obstacles easily. Design and weight distribution makes the difference.

Backpack vacuums now weigh in at less than 10 pounds, with suspension systems that distribute the weight across the hips for better balance and maneuverability.
Myth No. 8: Suction alone makes a vacuum work well. Actually, it's the entire vacuum system that determines its effectiveness.

Four key benchmarks are used to evaluate a vacuuming system:

Airflow
Airflow is the amount or volume of air moving through the vacuum, usually measured in cubic feet per minute (CFM). The amount of air moving through a vacuum affects the amount of soil that can be carried along by the airflow and contained in the vacuum's filtration.
Lift
Lift, also known as static lift or water lift, is the ability of the vacuum's airflow to lift dirt. It typically is measured in “inches of lift” determined by how many inches the vacuum cleaner's airflow can pull water up a tube in a lab test.

The higher the airflow and lift, the better; this combination largely determines the vacuum's ability to pull “particles in.”
Filtration
Filtration captures the soils and is mainly responsible for reducing “particles out.” Filtration must be designed and proportioned to work with the vacuum's airflow and lift so that the particles are stopped, but not the airflow.
Design
In some cases, good vacuuming potential and filtration are defeated by poor design. Examples of poor design include a tool orifice that lowers air velocity by being too wide (many beater brushes require an excessively wide tool orifice that reduces suction significantly) and body tolerances that allow dust to leak from non-filter areas.

The Venturi principle

Understanding the Venturi principle is important. It causes air velocity to increase as the corridor it passes through narrows. That explains how suction-only backpacks that use a narrow tool opening or orifice enable greater suction. They enable effective cleaning of plush carpet by proportioning the orifice opening and beater brush to allow the rotating brush to perform well while maintaining proper airflow and lift to remove soil and prevent its being driven airborne.

NOTABLE

23,787
National median square footage maintained per full-time custodial worker.
175.44
National median square footage maintained per student.
48,000
National median square footage maintained per building.
7.70
Percentage of total district expenditures spent by school districts in 2004 on maintenance and operations.