The Four Seasons Hotel Boston is a 13-story structure built in 1985, including a spa, pool, and fitness facilities. It overlooks the famed Public Garden and Beacon Hill, within easy reach of the financial and theater districts. The hotel's fine dining room, Aujourd'hui, is considered one of the city's best restaurants.

In 2003, the Four Seasons Hotel Boston began work on an extensive renovation of its first and second floors, adding a courtyard and expanding the two kitchens that served its two restaurants: Aujourd'hui, and the more casual Bristol. Its previous kitchen did not include a system that eliminated cooking odors, smoke, and grease emissions before being released into the atmosphere.

Like A Good Neighbor

In completing the renovation, Four Seasons had multiple requirements. Although the existing facility was being expanded, space for the unit and the connecting ductwork would be an issue. Odor wasn't the sole problem; smoke and grease emissions were also a concern. Four Seasons needed a system that removed these potential pollutants. Because Four Seasons caters to its guests 24 hours a day, minimal downtime for routine cleaning was a necessity. The system also needed to comply with strict federal, state, and local environmental standards, and finally, O&M costs had to be minimized.

In early 2003, Boston Properties had been involved with renovation work at the Prudential Properties, near the Prudential Center. This renovation project had required the use of a state-of-the-art kitchen emissions control system. Boston Properties asked TMP Consulting Engineers to conduct a full-scale review of all the products available for use. The review lasted three months, after which three options were presented to Boston Properties. Boston Properties chose United Air Specialists' Model PSG Smog-Hog system.

So when Boston Properties began work on the Four Seasons renovation, it already had a successful track record with one system. Rather than conduct another wide-ranging product review, it simply told TMP, "Get us another just like it."

With 99.9% efficiency, United Air Specialists' PSG system uses electrostatic precipitation (ESP) technology to filter emissions. ESP also electrically charges microscopic contaminants and captures them magnetically in an aluminum collection cell, releasing only clean air from the system. Exhaust ducting from the kitchen hoods carries the cooking emissions, grease, and odors first to a baffle diffuser, which separates the large particulates. "We joke that it will catch the chef's hat," says Mike Smith, UAS applications engineer for kitchen emissions systems.

The ESP collector then draws the contaminants onto aluminum collection plates within the system; the plates are closely aligned to improve collection efficiency. During this stage, some residual odor may pass through the collection cell, so a V-bank configuration of carbon filters removes remaining odors, releasing only clean air through the discharge.

For routine maintenance, the system is shut down for one hour every 24 hours for a self-cleaning cycle. An in-place, fixed-face, overhead washer cleans collection components without removal.

Creativity Required

"We allowed the system to be located in the space available, not just where the grease ducting happened to be," said Noel Metcalf of NR Metcalfe, the sales rep for UAS in the region. "We designed around the space they gave us," said UAS' Smith.ES