Chinese Drywall --- Demolition is NOT the answer

The following is a review of the theory behind Filter Scientific Coating’s Interceptor coating system designed specifically to address the issues of odor and off-gassing presented by tainted drywall.  

Case Summary: Our research team has been studying the odor and off-gassing properties of the tainted Chinese Drywall.  During this time the Filter Scientific Coatings research team has developed a coating system that provides continuous interaction with the tainted drywall. Since the installed drywall cannot be pressurized during ClO2 gas treatment or heated to temperatures high enough to induce an effective and thorough “bake-out” of odorous and off-gassing elements, the tainted drywall treated by these methods will continue to emit sulfur based gasses and related odors into the living environment. The characterization of the tainted drywall is a difficult task.  There are two basic chemical phenomena related to this drywall.  One is the issue of off-gassing which originates with the detection of various sulfur based gasses causing odor and believed in some cases to contribute to a mildly corrosive atmosphere in the presence of moisture.  It is unknown where in the off-gassing cycle the tainted drywall is from sheet to sheet or lot to lot as it was delivered to the US since 2003.  The second issue is that of odor produced by sulfur based gases.  As the off-gassing of the drywall begins to taper off over time, the odor left in the board builds and plateaus to a very long life cycle.   The tainted Chinese drywall has been tested by accredited labs in the US noting that the odor related to the Chinese drywall is in fact in the form of di-hydrogen sulfide, carbonyl sulfide, and carbon disulfide, among others. Given these facts among unknown rates of off-gassing and the varying life cycles of odorous effects, the Filter Scientific Coatings’ Interceptor coating system was specifically formulated to address off-gassing and related odors by providing a coatings matrix to promote absorption and neutralization of these effects by various techniques of chemical adsorption and use of ion exchange affinities at the molecular level. 

 The Filter Scientific Coatings – Tainted Drywall Coating System:  

â–  Theory for the Interceptor Coating System Development   

The gases and odors emitted from the tainted drywall will follow the laws of diffusion meaning they will migrate from areas of higher concentration to that of lower concentration.  The sulfur gases from the drywall are migrating toward the interior of the building structure (living quarters) as well as into the stud cavities.  For a specific sheet of drywall, the area associated with the living quarters versus the stud cavities would have a near equal amount of sulfur based gasses emitted into it, but would show less concentrated effects due to a larger volume of air spaced that is replenished.  The corresponding stud cavity area, in theory, would have a higher concentration of the sulfur based gases due to limited space and replenishment of air. Migration of the sulfur based gases from the interior of the tainted drywall occurs at any seasonable temperature and humidity level, but is most active at temperatures above 80F and relative humidity readings above 50%. Interesting is the notion that sealant technology for the drywall will eliminate the off-gassing and its odorous effects.  If this concept were true, then the original layers of paint used on the tainted drywall would have worked given that paint films are slightly semi-permeable membranes with perm ratings in the 4 – 8 perm range.  One would expect this to seal the drywall at least on one side, but the gasses and odors migrated through.  The Interceptor coating system functions in an opposite manner with a perm rating of over 40 perms by allowing the emitted gasses and odors from the tainted drywall to migrate into the matrix of the coating for neutralization and adsorption. The Interceptor coating system designed to be applied to the surface of the drywall in the living quarters’ spaces and injected into the stud cavities is formulated with enough active ingredient to neutralize sulfur based gases and odors if it were theoretically possible for all elemental sulfur contained in the calcium sulfate (gypsum) for a given area of drywall to convert to sulfur based gases.  The premise is for the Interceptor coating system to provide a suitable matrix on both sides of the drywall that has sulfur based gases chemical and related odor adsorption capacities magnitudes greater than the drywall’s capacity to produce such gases and odors. Additionally, instances of total drywall removal in certain homes / buildings have shown continued odorous effects.  Absorption of the sulfur based gaseous odors is greatest on metal stud networks and oriented strand board (OSB) sub-flooring.  The zinc based coating on the metal studs absorbs the sulfur based gases and show a higher degree of odor than wood stud networks.  The resin based binders used to bond OSB together are very moisture sensitive and their hygroscopic nature promotes migration of the sulfur based gassed emitted from the drywall into moist air that eventually migrates into the sub-flooring via natural fiber based carpet backings and underlayments. 

 â–  Interceptor OC – Water-based Surface Coating  

 Interceptor OC is a water-based coating designed to provide an absorbent dry film matrix when applied to the surface of the drywall.  Sulfur based gases and odors emitted from the tainted Chinese drywall are absorbed into the matrix and are neutralized by chemical adsorption.  The dried coating matrix has a perm rating of over 40 perms which allows the off-gassed elements to migrate into the coating.  The molecular pathways within the dried coating matrix provide access to adsorption sites where the neutralization of gases and adsorption of odors occurs.  The sulfur based gases are bound at a molecular level to form inert molecules, whereas their odorous effects are bound chemically in a similar manner.  The affinity of these sulfur based gases and odors for these adsorption sites is greater than their tendency to be released from these adsorption sites at all applicable temperature, humidity, and atmospheric conditions. The Interceptor OC coating is designed for use where water-based coatings are allowed to dry properly.  They exhibit excellent adhesion and durability to drywall, wood, metal, and masonry among other surface types.  Use on stud networks, masonry and sub-flooring is recommended in situations where complete drywall removal has been done. 

â–  Interceptor EX – Confined Space Powder Coating 

For concealed spaces behind the drywall, the Interceptor EX powder coating is electro-statically charged promoting adherence to all surfaces inside the confined space of the wall cavities.  Through a static discharge unit, Interceptor EX is injected into the stud cavities and is activated to adhere to interior surfaces by an electrostatic dipole formed during the injection process.  This electrostatic charge helps overcome the forces of gravity keeping these powder coatings in place once adhered to a surface within the stud cavity. By injection, the powder coatings are thoroughly dispersed throughout the stud cavity to maximize coverage within that space.  In instances where dispersion is limited, these powder coatings are designed to take advantage of concentration gradients within the stud cavity.  Interceptor EX is designed to adsorb the sulfur based gases and related odors when completely dispersed or when pocketed into certain sections of the stud cavity.   The concentration of the sulfur based gasses and related odors emitted into the stud cavity are reduced over time as they are absorbed into the molecular matrix of the powder coatings.  As this absorption occurs and results in chemical adsorption, the concentration with the stud cavity is reduced causing remaining odor and gas molecules to spread and even the concentration gradient within the confined space.   As a result, additional gas and odor molecules are absorbed into the powder coating and then adsorbed.   The Interceptor EX is designed to optimize absorption in high humidity regions of the US.  High humidity can impede molecular adsorption if not addressed.  The powder coating is a complex combination of materials tested under extreme heat and humidity for the control of odor and reduction of sulfur based gases in confined spaces. The sulfur based gas adsorption capacity of the Interceptor EX is tested by metered air flow tests to determine the grams / cc adsorption limits of the coating.  Additionally, as the drywall ages, it will continue to off-gas into the stud cavity raising the concentrations of the sulfur based gases and odors again and again until its tendency to do so tapers.  The recommended volume of Interceptor EX used in a given confined space will continue to absorb the sulfur based gases and related odors exceeding the tainted drywall’s capacity to produce such gases and related odors. 

â–  Ecological Design 

The Interceptor coating system for tainted drywall is designed to support the most current “green” initiatives for the construction industry.  This environmentally friendly coating system is non-carcinogenic, formaldehyde free, halogen free, solvent free, and low VOC.   The Interceptor OC water-based surface coating system also provides flame retardant properties by enhancing the flame barrier character of the coated surface with a protective char matrix when exposed to direct or indirect flame.     The chemical entities resulting from the absorption and neutralization process designed as the function of the Interceptor OC / Interceptor EX coating system are inert and non-reactive materials thereby terminating propagation of the continued effects characteristic of tainted, sulfur-based gas and odor emitting drywall.    

 â–  Additional Comments – Testing for sulfur based gases 

The Interceptor OC / Interceptor EX coatings have been tested in multiple repeated tests for twenty sulfur gas species to determine if these airborne contaminates are and continued to be absorbed and controlled by the coating system.  Results have shown undetectable levels of the following: 

Di-hydrogen sulfide                             Isobutyl mercaptan

Carbonyl sulfide                                  Di-ethyl sulfide

Carbon di-sulfide                                 n-butyl mercaptan

Methyl mercaptan                               Di-methyl Di-sulfide

Ethyl mercaptan                                  3-methyl thiophene

Di-methyl sulfide                                  Tetrahydrothiophene

Isopropyl mercaptan               2,5-Di-methyl thiopheneter

-butyl mercaptan                2-ethyl thiophene

-propyl mercaptan                           

Di-ethyl Di-sulfide                     Ethyl methyl sulfide                             Thiophene 

Given that the half lives of these gases differ greatly, the three main gases including di-hydrogen sulfide, carbonyl sulfide, and carbon disulfide have been tested within the half life limits repeatedly to insure consistent results within and among test sites. When determining the activity of the drywall, test lab analysis will involve analyzing the gasses emitted from ground gypsum from the interior of active drywall samples.  This material is heated in a confined chamber and analyzed for sulfur species.  Repeatedly, the active drywall normally exhibits concentrations, according to this test, of at least 1 microgram / kg of H2S gas, with the most active drywall near 5 micrograms / kg of H2S gas.  Lower levels of C2S and COS gases are also detected in active drywall.  

 â–  Additional Comments – Question of Corrosion

 Accredited laboratory testing of the Interceptor coating system applied to tainted drywall with H2S activity of 5.1 micrograms per gram has confirmed under long term accelerated ageing conditions of 95F and 85% RH that the coating system is controlling the corrosion of copper versus uncoated tainted drywall control samples. All copper will eventually tarnish.  The differences between corrosion and tarnishing are important concepts.  In a complex process of controlling and adsorbing gases that can convert to dilute acids in air, a tarnished copper surface in the presence of the Interceptor OC / Interceptor EX system, and more specifically the chemical nature of the tarnished surface, can differ greatly from the surface of copper tarnished or corroded in an environment with tainted Chinese drywall that has not been coated. Lab testing has also shown under long term high heat and humidity, copper pipe exposed to tainted Chinese drywall becomes grayish-black with a frosted look.  Whereas, copper pipe exposed to tainted drywall coated with the Interceptor OC / Interceptor EX system exhibit reduced tarnishing effects.  Thank you for your interest.  If you have additional questions, please let us know.  We look forward to meeting you soon!  Sincerely, Filter Scientific Coatings