[design '98]

Keeping dust down during healthcare construction

Coffman Engineers

Most healthcare facilities are ongoing construction sites these days, with constant repairs, renovations and additions as hospitals respond to innovations in technology. So there's no harm in a little construction dust floating around, right?

Wrong. Just in the past three years, scientists have discovered that dust is a very effective transporter of airborne bacteria. Many hospital deaths are attributed every year to dust-borne diseases such as Aspergillus. It's not that the dust itself is dirty - just that the particles give a free ride to bacteria looking for weak and vulnerable hosts. Recent discoveries linking patient deaths directly to contamination from construction dust have heightened national awareness about this problem. So the engineering community is now being asked to help hospitals take precautions to stop the spread of construction particles in healthcare facilities, primarily with sophisticated pressurization techniques.

Aspergillus: A real danger

Aspergillus a mold that is common in the natural environment. But it causes an invasive disease in hospital patients called Aspergillosis, which looks and behaves much like tuberculosis. It can infect the sinus, ear, lung, central nervous system, prosthetic cardiac valves, gastrointestinal tract, bone and skin. Symptoms include fever, cough, and sputum with blood and flecks of white or brown fungus material.

According to the latest research conducted at Northwest Memorial Hospital in Chicago, as many as 30 percent of all fatal infections among patients with acute leukemia and lymphoma are believed to be caused by the fungi.

Other patients at high risk are those in intensive care units, newborn nurseries (especially neonatal intensive care and dialysis units), operating rooms, and invasive procedure areas. Clearly, these patients must be protected from dust sources that could bring unwanted bacteria.

The power of air pressure

Many rooms in hospitals are typically pressurized, to control the spread of infection. Operating rooms, for instance, are designed with very ``positive'' air pressure, meaning that there is more air supplied to the room than is removed from it. When a door opens, air rushes out, rather than in. This serves to protect patients from infection by keeping the site of the wound clean and discouraging the influx of new germs.

Turn this idea on its head, and you have the concept behind negative pressurization for construction sites. If the work area has a lower air pressure than adjacent areas of the healthcare facility, then air will rush in, not out, keeping dust particles from escaping. The same principle is used in isolation rooms, by the way, to prevent the spread of infectious diseases like tuberculosis. Pressurization involves much more than just turning on a fan.

Round-the-clock monitoring devices track pressure levels at the construction area and signal an alarm if pressurization levels are not maintained. Some hospitals continuously record pressurization levels, to reduce the potential liabilities of the contractor and hospital.

Special air flow systems establish negative pressurization at hospital construction areas. Typically, air is drawn from the construction area and blown to the outside through filters, which capture dust for proper disposal. This is accomplished using dedicated fans serving only the construction area.

Wipe your feet, please

People carry dust on their clothes and bodies, and dust could easily hitchhike on building materials being brought in and out of the construction site. So precautions are taken not just at the work area itself, but also at entry points for workers and their supplies.

Workers create a barrier for the construction area within the hospital, using visqueen (plastic sheeting), or plywood to produce a pressurized room, similar to an airlock. Once inside the airlock, workers put on disposable overalls, or discard them for street clothes, and step on special sticky mats to remove any particles clinging to their shoes. Fans and filters in the airlock seize dust particles from clothes or materials, and prevent them from floating to occupied areas of the hospital.

Low-tech logistics

Now that the dangers of Aspergillus and other airborne bacteria have become well known, it makes sense to combat them using every tactic available - including low-tech traffic planning.

Controlling air pressure in construction areas helps contain dust -- and combats the spread of deadly infections like Aspergillus, which can be carried on dust motes to patients throughout the hospital.

Special attention is now given to the delivery of construction materials, and minimizing points of entry and exit. Can boards, conduits and fixtures go in a window instead of through the hospital? Can one elevator be devoted to construction usage for the duration of the project? Can a dedicated delivery route be created, where hospital patients, visitors and staff will have little or no contact with construction materials? Can construction trash go straight to a truck through a chute, rather than being carried by hand down a hall?

All of these practices can be very effective in keeping the rest of the hospital dust- and danger-free.

Renovation: Respecting resident patients

Controlling dust is both important and difficult when renovations occur near occupied areas in a facility. Consider the typical case of a hospital when remodeling patient rooms on one floor of the facility. The renovation usually requires extensive plumbing work through the floor, into the ceiling space below.

The floor below may be occupied by patients, for example, in a critical care unit and it may be impossible to move them to allow for construction.

These patients must be protected from contamination of any kind. So, working as a team, the hospital, the contractor and the engineers must work out a plan of action to vacate one room at a time.

Workers seal off each room with visqueen sheets, creating a negative space with fans and filters discharging through a window. This permits workers to complete their tasks on the plumbing above without compromising the well-being of the patients in adjacent areas.

Hospitals throughout Washington are adopting the new dust-control measures during construction. They include Sacred Heart Medical Center in Spokane, Harrison Hospital in Bremerton, St. Joseph's Medical Center in Tacoma, Good Samaritan Hospital in Puyallup, and Stevens Hospital in Edmonds.

Given the rise in infectious diseases in our region - especially new strains of tuberculosis that are resistant to antibiotics - we will see the proliferation of these and other dust-control practices in hospitals and other health care facilities. So if you're planning to enter a healthcare construction area in the near future, get ready to dust off, suit up, zipper yourself into an airlock.

Robert E. Rosenbaum is senior project manager in the mechanical engineering department at Coffman Engineers.

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