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Black Mold Removal – Using Dry-Ice Blasting

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Dry-Ice Blasting for Mold Remediation

Dry ice blasting accomplishes mold remediation more completely than mechanical abrasion. Dry ice blasting does not require chemicals and does not create a toxic dust hazard from mold remediation operations, such as, when manually scraping and sanding. The range of available nozzles for dry ice blasting equipment enables us to access tight corners, and in many cases, clean mold from areas inaccessible to hand tools, such as inside corners of wood framing trusses and joists.

Note: Mold remediation to attic ceilings with deep mold staining is best accomplished with our chemical method versus dry ice blasting. This is because dry ice blasting cannot penetrate deep enough into the wood to remove the dark mold stains.

Dry-ice is Safe on Electrical

Dry-Ice Blasting is a non-conductor of electricity, so live electrical equipment and wiring does not have to be removed or de-energized during the remediation process. Dry Ice Blasting leaves a dry surface, eliminating the need for drying downtime and making it safe on electrical components and wiring, junction boxes, power panels, ductwork, and plumbing.

Dry-Ice Blasting Before & After Pictures on a 7/2019 attic mold remediation job this attic ceiling had a high level of aspergillus mold growth

Attic Ceiling Mold Removal – Before Pictures

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Attic Ceiling Mold Removal - After Pictures (same attic)

Dry-Ice Blasting - How it Works

Dry ice blasting for mold remediation uses four physical properties of air-propelled dry ice pellets: velocity, abrasion, thermal shock, and evaporation. Dry ice is solid (frozen) carbon dioxide. For blasting uses, dry ice is manufactured in pellets of various sizes appropriate to the substrate to be cleaned. The pellets are hurled from a blasting gun by air pressure, which provides the velocity. When the pellets strike the surface to be cleaned, three things happen. First the velocity of the pellet strikes the substance to be removed. Because dry ice is at a temperature of -109 degrees F., the thermal shock helps loosen and lift the substance to be removed. Finally, the dry ice pellet flashes into carbon dioxide gas, providing more lift to the substance to be removed. The carbon dioxide gas is harmless, leaving no cleaning material such as sand or solvents to be cleaned up after the cleanup.
Complete mold removal and remediation requires solving the moisture problem that enabled the mold to grow in the first place. A mold needs food, such as wood; moisture; and a temperature range favorable to the growth of the specific mold organism. Grinding, sanding, or wire-brushing to remove mold growth does not sanitize the surface and kill the mold spores. Without dry-ice blast cleaning, a biocide/sanitizer/cleaner is needed to kill the mold spores. Dry ice blasting will almost rid the need for biocides and thus, enhance occupant and worker safety. Its a great option for mold remediation in areas with a chemical sensitive individual.

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high density dry-ice pellets

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Dry-Ice Blasting for Fire Damage Restoration

Dry Ice cleaning is also extremely effective in removing toxic residues, such as, soot and associated smells after a fire. The Dry Ice Blasting produces a more thorough cleaning by reaching areas other methods cannot. The blast stream reaches the smallest cracks, creases and wood joints where wire brushes or hand cleaning cannot. This allows for a better evaluation of the damage otherwise hidden by smoke or soot, which is important after a fire for structural inspection, health and general maintenance.

 

Dry-Ice-Blasting – Technical Information

 

Pellet Kinetic Energy

The dry-ice blasting process incorporates high velocity (supersonic) nozzles for surface preparation and coating removal applications. Since kinetic impact force is a product of the pellet mass and velocity over time.

Even at high impact velocities and direct head-on impact angles, the kinetic effect of solid CO2 pellets is minimal when compared to other media (grit, sand, PMB). This is due to the relative softness of a solid CO2, which is not as dense and hard, as other projectile media. This characteristic is a plus. This prevents damage to the wood surfaces and electrical wiring. Also, the pellet changes phase from a solid to a gas almost instantaneously upon impact, which effectively provides an almost nonexistent coefficient of restitution in the impact equation. Very little impact energy is transferred into the coating or substrate, so the blasting process is considered to be nonabrasive.

 

Thermal Shock Effect

Instantaneous sublimation (phase change from solid to gas) of CO2 pellet upon impact absorbs maximum heat from the very thin top layer of surface coating or contaminant. The very rapid transfer of heat into the pellet from the coating top layer creates an extremely large temperature differential between successive micro-layers within the coating. This sharp thermal gradient produces localized high shear stresses between the micro-layers. The high shear produced over a very brief expanse of time causes rapid micro-crack propagation between the layers leading to coating final bond failure at the surface of the substrate.

 

Thermal-Kinetic Effect

The combined impact energy dissipation and extremely rapid heat transfer between the pellet and the surface cause instantaneous sublimation of the solid CO2 into gas. The gas expands to nearly 800 times the volume of the pellet in a few milliseconds in what is effectively a “Micro-explosion” at the point of impact.

The “Micro-explosion,” as the pellet changes to gas, is further enhanced for lifting thermally-fractured coating particles from the substrate. This is because of the pellet’s lack of rebound energy, which tends to distribute its mass along the surface during the impact. The CO2 gas expands outward along the surface and its resulting “explosion shock front” effectively provides an area of high pressure focused between the surface and the thermally fractured coating particles. This results in a very efficient lifting force to carry the particles away from the surface.