Dry ice blasting is rapidly becoming a much preferred procedure for getting rid of mold. This technique is superior to cleaning mold through conventional means such as wire brushes, scrapers and sanders, all of which require considerable physical effort. The dry ice technique cleans just as well or even better than the traditional cleaning procedures and takes a drastically reduced amount of time to do so. Comparing it with soda blasting, it does a job just as good without creating as much mess. Check out another great tool for mold prevention and dust mite cleaning.
Dry Ice: a Quick Overview
Liquid carbon dioxide, taken from a pressurized storage tank, and expanded at ambient temperature to yield snow, is the process by which dry ice pellets are made. Next, this snow undergoes compression using a die to create the hard pellets. These pellets can be easily acquired from the majority of dry ice suppliers in the country. The normal size for dry ice blasting is 1/8’’ high density pellets.
How Does Dry Ice Blasting Work?
This process involves a blasting gun firing rice sized dry ice particles at supersonic velocities to strike and clean a surface. Compressed air is used for acceleration of the particle, similar to other blasting mechanisms. When the dry ice strikes the surface, it goes directly from being a solid to being a gas (it sublimates). The substrate (in this case, the surface) is left clean of any mold spores.
Three phases are involved in this process. Energy contained in the accelerated dry ice pellets is transferred to the surface on impact which is responsible for knocking off the mold without damaging the surface underneath.
A micro-thermal shock is created as the pellets, having a temperature of -79C, strike the contaminant. This shock is created between the mold and the surface beneath it. The thermal shock doesn’t do much in the way of removing the mold, as it does with waxes, oils, resins, food particles etc. – where it results in cracking, delamination of the contaminating material, aiding in its removal.
The last phase, gas pressure, sees the pellets explode upon striking the contaminant, and as they warm, they change into carbon dioxide gas – basically a volume expansion with a factor 400 to 800! The rapid expansion beneath the contaminant forces its removal from the substrate from behind. The contaminant becomes relocated i.e. airborne as a result of the energy transfer / gas pressure action and has to be removed using HEPA filters. Because the dry ice itself has turned into a harmless gas at this point, no cleaning up is required for it.
The air system for dry ice blasting applications is typically between 80 – 100 PSI, 120 – 150 CFM. It is recommended that the air system be evaluated to ascertain whether the facility can successfully run the dry ice blasting system at the level required for the removal of mold.
Typically, dry ice blasting does not change the mold removal procedure by a great deal. Considering the example of a second floor home with drywall walls, no attic and a ceiling with a mold growth, the remediator would first cut off the second floor from the first after which they would develop a negative pressure via an air scrubber (HEPA filtered). At this point, any heavily damaged carpeting / drywall would be double bagged and then disposed. In this example, half of the ceiling, as well as all of the exterior drywall had to be removed.
Now, the home is ready to be cleaned using dry-ice blasting which is applied to the support beams and plywood. The blasting gun is set to aim at the required mark and voila. The process can be streamlined further by using application specific nozzles for cleaning the wood. The dry ice pellet’s action on the mold covered wood is clear and methodical. After the blasting phase, the surfaces are vacuumed and saw dust / other debris removed. Lastly, the remediators apply a micro-biocide spray on the cleaned areas to prevent future mold growth.
When using this technique in tight areas e.g. crawl spaces, the air level should be maintained carefully. In some cases, supplied air respirators might be needed. Refer to the OSHA Permissible Exposure Limit for carbon dioxide to determine whether this is the case. Moreover, since the process is noisy, ear protection is needed. Also, the -79C temperature of the dry ice necessitates the use of insulated gloves. It goes without saying that complete personal protective equipment be worn.