HOW MANY HOUSES, IN HOW MUCH PERIL?

Byline: AARON KESSLER

In the spring of 2006, the cargo ship Great Immensity headed toward Florida's west coast. Its destination? the Port of Tampa.

In its hold? More than 16 million pounds of Chinese drywall manufactured by Knauf Tianjin -- enough to potentially make more than 1,700 homes.

The Great Immensity's shipment was one of hundreds that have arrived on American shores since January 2006, a Herald-Tribune analysis of shipping data shows.

All told, at least 550 million pounds of Chinese drywall have came into the United States since 2006. With that quantity, some experts say, you could construct 60,000 average-size homes.

Builders who used the material, like Miami-based Lennar Corp., acknowledge that the gases being emitted from some of the Chinese drywall are the cause of the corrosion eating away at the guts of homes. The gases have blackened metal components such as coils and wiring. Homeowners have reported televisions, computers and other electronics failing, and even silver jewelry turning black.

But Lennar, other builders and at least one of the manufacturers point to scientific tests they commissioned showing that the amount of sulfur compounds being emitted is below the amount that federal guidelines say could endanger human health.

"What we aimed to do is figure out whether the air inside those homes was a health concern, and we found there was none," said Robert P. DeMott, managing principal of Environ International Corp., which conducted the investigation for Lennar.

Residents, some with small …