By: Licensed Mold Assessor Brad Fishbein
February 11, 2023
There are many different known methods to kill mold. While killing mold is not necessarily always the goal (removing it may be necessary) there are certain methods to get rid of mold that are better than others.
Extreme heat treatments are known as a good way in killing mold growth but what about the opposite?
Does freezing mold kill it?
No, freezing mold does not kill it, but instead keeps it dormant. While freezing temperatures can cause mold fragments to become inactive, the spores can reactivate and grow again once the temperature rises. According to the CDC's Procedure for Preserving Yeast and Mold Isolates, mold can be preserved at a temperature of -70℃ (158℉) to maintain its long-term viability. Thus, simply freezing mold is not enough to eliminate it and the best way to kill mold is to clean and remove it completely using appropriate cleaners and procedures and to fix the underlying moisture problem that led to the mold growth in the first place.
So let's explore how freezing is a method to make mold issues disappear.
Mold grows in specific conditions of the right temperature (extreme temperatures can suppress mold growth), sufficient moisture (relative humidity under 60% can help prevent mold), and a good food supply (mold needs porous materials to grow on).
If all those conditions are not met, an indoor mold-infested colony cannot thrive or even exist.
That could be where freezing can come into effect to control mold growth.
As stated earlier, you can't just use regular ice. With humid and warm air, regular ice of course melts. And once the ice melts, it obviously turns to water which will help mold grow.
A more efficient method is using the dry ice blasting method.
If you are unaware of what dry ice is, it's frozen carbon dioxide. And when it melts, it does not melt into liquid but turns into gas.
Using the dry ice blasting method combines high pressure and speeds with low temperatures to detach the mold from the surface. Temperatures could be as low as -70℃ (158℉) degrees to remove mold spores.
Dry ice-blasting mold allows experts to remove them from hard-to-reach areas like in-between boards or wooden pieces. Removing the mold from wooden surfaces takes less time and has more significant results.
Despite being a non-contact and non-corrosive method, if the high pressure and low temperature are misused could affect the surface of the molds. The low temperature destabilizes the mold infestation while using high pressure to detach from the surface and eliminate it.
And while fragments of the dead mold are still present and need to be cleaned, without moisture buildup and humid air, all the dead mold will stay dormant.
Using dry ice when removing mold has its benefits and challenges. Mold spores can be cleaned quickly and efficiently with proper training and equipment. Different types of molds may present themselves in different areas. Here are some reasons why dry ice should be used to make mold die.
Certain species of mold can produce mycotoxins that could possibly affect the air quality in the home. Using mold killing cleaners that have toxic substances when treating mold can be dangerous. Dry ice can be, as well if done in an area that is not properly ventilated.
Think of it as being in a car with the garage closed. Air circulation is necessary or it can be lethal.
But once that carbon dioxide clears out of the badly ventilated area the area is safe again whereas using a harsh substance such as bleach to kill all the mold can be dangerous for a longer period of time after it is used.
Dry ice blasting involves using specialized equipment to move ice pellets at high speed and pressure to offset the mold spores from the surface. This process protects the surface from excessive chipping and trails of secondary wastes.
Being a non-contact method makes it safe for the surface and the handler. This process eliminates the need for close contact and handling, which could be a potential risk.
Dry ice blasting is quite effective. The freezing temperatures and high pressures ensure the mold spores get lifted off the surface without leaving a lot of secondary waste.
It comes highly recommended by industry experts because of the results' quality. The time taken, the experts required, and the area covered during the mold removal affirms its effectiveness. Using cold temperatures with dry ice is great in areas where mold thrives like in a crawl space or attic if there is enough space for the blaster.
Dry ice blasting is a technical process incorporating temperature, pressure, and speed to uproot mold growth from various surfaces. You can use it on different surfaces indoors and outdoors with significant effect. However, you must have trained experts to manage the process successfully. In order to control mold proper technique must be used.
The ice pellets can usually permeate through a surface, thus removing the molds without affecting the surface appearance or integrity.
This abrasive method doesn’t affect the composition and structural integrity of the surface. For example, only about 3% of a wooden surface might get chipped off during the process showing its gentleness on the surface. Of course, if a surface is temperature sensitive, freezing temperatures may not be the best option!
Dry ice blasting takes a shorter time to cover a larger mold-infested area. For example, depending on the size of the home, it only takes at least two days to clean the house's sheathing from supports and beams. This could take up to 5 days to complete the removal through sanding.
Using dry ice can complicate mold removal because it requires specialized tools and trained personnel to complete the task. Mold remediation companies take their time (or at least they should!) to take their experts through dry ice-blasting training to ensure quality results for the clients.
Having a blasting gun with different nozzles helps reach other areas and surfaces. For example, a fan-shaped nozzle is used for boards and beams. This nozzle can also create a specialized effect or remove stains on wooden surfaces improving its appearance.
Dry-ice blasting can be effective but there are certain times when it should not be used including:
While blasting the moldy surface while removing the appearance of mold with cold temperatures, if the source of what caused mold in the first place is not addressed, carbon dioxide will not prevent mold growth in the future.
Dry ice should not be used to drywall that has been water damaged. Organic materials with enough moisture damage should be removed and not treated. Dry-ice blasting is best used on structural building material that has to remain in place such as roof sheathing or subflooring.
Ice blasting combines several techniques to detach and remove molds from surfaces. Because carbon dioxide can be dangerous and dry ice can be harmful to the skin, it is not recommended that a normal person use this method to kill mold.
Dry Ice blasting should be left to be done by professionals with proper training in removing mold using freezing temperatures and dry ice.
Dry ice blasting involves using ice pellets as the medium at high speeds on mold surfaces. Dry ice is frozen carbon dioxide. The acceleration of these ice pellets onto a surface lifts the molds from the surfaces stimulating their removals. Since the pellets are different sizes and blasted from a gun, the air pressure difference created uproots the molds quickly and effectively.
The friction created when the pellets drive onto the moldy surface rubs and clears the surface. The kinetic energy generated breaks the bond between the mold and other substrates. The pressurized air stream also helps in removing stains on the surfaces and makes mold die.
Thermal shock in the process results from the low temperatures in ice pellets (-110 degrees). These temperatures will make mold dominate, thus dissociating it from the surface. It loosens and then will send mold spores off the surface.
Once the dry ice gets blasted from the gun onto the surface, it changes to a gas as we said earlier. This change increases the volume of the pellets over the mold-infested surface, increasing the surface area it covers. The impact is increased abrasion over the entire surface over a short period.
The gaseous mixture provides a medium in which the detached mold can move over the surface, reducing the secondary wastes from the process. Additionally, since dry ice evaporates, there's no worry about extra debris from the abrasion process that could require additional tasks in cleaning up.
Dry ice blasting is a straightforward process involving these three steps:
Non-infested areas will need to be covered. A containment barrier using 6 mil plastic will prevent mold growth on other non-affected items nearby.
If it’s a closed area like an attic, the openings should be sealed into and out of the attic.
Areas with the highest moisture content will have There’re special nozzles that cater to areas in corners or hidden areas behind beams. Then, get the containment or the negative air for your blasting process. Set up your equipment as you put on your safety equipment, ready for the job.
The blasting part is pretty straight forward.
Areas with stains may require a higher blast for more mini explosions to brush off the stains.
There may be sawdust or wood chips after blasting. If a containment barrier is used clean up should be simple for the mold professional.
The area should then be cleaned using a HEPA vacuum.
Some mold professionals will also use and anti-fungal application in addition to ice blasting after clean-up is done. Certain solutions can leave a film that can help prevent mold in the future.
Ice blasting is slowly gaining popularity in the mold industry because of its excellent results. Here are some benefits of using dry ice blasting: It’s a straightforward procedure where you can make mold die and remove it on structural surfaces.
Meet the author: Brad Fishbein is an ACAC council-certified Microbial Investigator. In the fall of 2012, he became a Licensed Mold Assessor in the State of Florida through the Department of Business & Professional Regulation. Brad has helped homeowners with over 5,000 successfully completed Mold Inspections since 2009.