The government isn’t quite done with its scientific investigation of metal-corroding, sulfuric-smelling Chinese-made drywall, but investigators say they know enough to recommend that the troublesome drywall, along with all the home’s electrical components, smoke and carbon dioxide alarms, and gas supply lines, should be ripped out and replaced

“Taking these steps should help eliminate both the source of the problem drywall and corrosion-damaged components that might cause a safety problem in the home,” said HUD and the U.S. Consumer Product Safety Commission said in an April 2 joint statement announcing the recommendations.

That doesn’t mean that there aren’t other ways to fix the problems, investigators said. “Less extensive or costly remediation methods may ultimately prove effective, but at present the task force lacks a scientific basis to evaluate those methods.”

The “interim guidance” was offered before the scientific investigation was officially finished because many homeowners with the problem drywall are anxious to correct the situation, but have been unsure about how to fix their houses.

It’s been a little longer than a year since the problems of sulfur-emitting Chinese drywall emerged. Homeowners began complaining of metals corroding in their homes, air-conditioning coils failing prematurely, and caustic smells that many said caused health problems. Now more than 3,000 homeowners from 37 states plus the District of Columbia, American Samoa, and Puerto Rico have reported having faulty drywall to the government. The majority of the complaints (59%) have come from Florida, followed by Louisiana (20%).

The investigating agencies have yet to make any pronouncements related to health concerns related to the Chinese drywall. In addition to noting a “rotten egg” smell inside their houses, consumers have reported irritated and itchy eyes and skin, difficulty breathing, persistent coughs, bloody noses, runny noses, recurrent headaches, sinus infections, and asthma attacks.

But the investigation has determined that the Chinese drywall imported during the housing boom and post-Katrina does emit more sulfur than drywall from North America and that the those sulfuric emissions are high enough to cause metals, including air-conditioning coils, to corrode.

Thirty samples of drywall, including some imported from China in 2005/2006 during the peak of the building boom, as well as drywall made in North America, were put in small “chambers” where their emissions could be measured. The top 10 sulfur-emitting samples were of Chinese origin, and some of the Chinese samples emitted hydrogen sulfide at a rate that was 100 times higher than the non-Chinese samples. (Hydrogen sulfide corrodes metals.)

“The patterns of reactive sulfur compounds emitted from drywall samples show a clear distinction between the Chinese drywall samples … and the North American drywall samples, except for two Chinese samples that have similarities to the North American emission profile," according to the report. Some drywall imported from China in 2009 showed markedly lower levels of sulfur emissions.

The agencies did note that its sample size was small, that it was testing unpainted drywall versus painted drywall in homes, and that its models on the impact of the drywall in homes ware based on estimates.

The studies did debunk one theory that Chinese drywall emitted more sulfur compounds because it contained bacteria that produce sulfur as a metabolic by-product. A sampling of 10 drywall samples showed no apparent difference in sulfur-reducing bacteria in either the paper or gypsum core samples between imported Chinese drywall and American drywall, according to the government.

Other parts of the home may have been corroded by the bad drywall, but don't necessarily need to be replaced, according to the government, because they don't pose safety problems. These include copper plumbing pipes and HVAC evaporator coils.

Finally, the guidance says there’s no scientific basis to believe that studs, flooring, or cabinets need to be replaced. While the government recommends that all drywall debris and dust needs to be removed from homes, it also says there’s no evidence that HEPA vacuums and ventilators need to be used during the replacement.

More test results assessing the long-term effects of problem drywall on the safe operation of electrical components, gas distribution lines, fire safety, and HVAC components is expected to be finished this summer.

While the government’s remediation guidelines are clear, the question of who is financially responsible for the cost of the fixes is not. Some home builders, such as Lennar, have voluntarily replaced the drywall in its affected homes and then are suing their suppliers. Others have reserved millions toward remediation. In the meantime, insurance companies are citing exclusion clauses in an effort to avoid paying claims, and lawsuits have begun to pile up, with several in courts now.

Teresa Burney is a senior editor for BUILDER and BIG BUILDER magazines.