Re: Re: Dry Ice Treatment

[Guest guest]

I may have mentioned in the past that the term " dry ice blasting " should be

changed to " dry ice treatment " for the following reasons: (1) Dry ice

blasting like sand blasting in my opinion is not a very professional use of

the term; and, getting paid for remediation artistry, no matter if it is the

cleanup of sewage or mold to fire smoke and soot odor; (2) Dry ice treatment

is an art where remediation jobs can be screwed up by the wrong application

or successfully completed, therefore, not everyone is qualified to do dry

ice treatment; (3) Dry ice treatment is a surgical approach to completing

remediation project that requires special care of the environment and health

remediation workers as Jeff Bishop pointed out.

Dry ice treatment is under utilized in our industry. It offers many

remediation benefits other treatment processes have a hard time matching.

Moffett

Re: Dry Ice

Emma

Of all the blast cleaning systems, I prefer dry ice. Having said that, I

have reservations about the use of blast systems being used in mold

remediation especially CO2 in confined spaces or in containment.

The following is a copy of a column that I wrote sometime ago for ICS

magazine. It addresses blast systems in general with some specific comments

about CO2. (my personal opinions)

Blast cleaning is a group of cleaning methods in which abrasive media

particles are introduced into an air (or sometimes water) stream, which is

then directed at a surface to clean it. There are many media types in use,

including soda (sodium bicarbonate), as you mentioned.

Media types include steel grit, water ice chips or flakes, plastic chips,

walnut shells, dry ice, sponges embedded with a variety of media, and

others.

In this article, we will first discuss the characteristics of blast cleaning

in general, and then those of two specific media.

Air pressure, volume, and the distance the media has to travel to the

surface after injection all significantly affect the aggressiveness of blast

cleaning methods, as do the density, hardness, weight, size and other

characteristics of the media used. The ability to adjust these many

variables individually makes blasting an extremely versatile system of

cleaning. Some blast methods are so gentle they can remove graffiti from

painted surfaces without damaging the paint beneath. Others are so

aggressive that they can deeply " profile " a steel plate surface for better

paint adhesion.

Two main uses for blasting have gotten a lot of attention recently in the

cleaning/restoration industry. These are: removing charred wood and smoke

residue from framing after a fire, and removing mold growth from wood

framing (and sometimes other surfaces) during mold remediation. In both

applications, blasting is very effective at thoroughly cleaning the

intricate surfaces which are so labor- intensive to sand, scrape or wire

brush manually.

When media blasting is used for these purposes, we should keep in mind what

blasting actually does. Most blast media will do a great job of removing

char, smoke or mold growth from wood framing.

However, when the contaminant comes off the surface, it does not disappear.

Instead, it aerosolizes and creates worker exposure levels that probably

exceed those created by any other method of cleaning.

High-pressure water washing is similar in many ways to blast cleaning

methods, using the water stream itself as a " blast " media. Air washing is a

method of cleaning that is essentially blast cleaning without any media.

Both, like blasting, do an excellent job of aerosolizing particles from a

surface, although air washing is often ineffective if the particles are

adhered to the surface. Air washing, using a variety of delivery mechanisms,

is often used as a component of air duct cleaning.

The aerosolization caused by blasting is not always a problem. For instance,

if mold remediation is done outdoors or in an unenclosed space such as a

structure that has not yet been closed in, the mold spores are able to just

disperse. This assumes unprotected people are far enough away as to not be

endangered and that contaminants are not being drawn into a building.

Contents can be effectively and safely cleaned using blast methods either

outside or in a true laminar airflow cleaning chamber.

There is another possible problem when blasting is used for mold remediation

or for cleanup of other types of potentially hazardous particles. Most mold

spores are 1–2 micrometers and larger. Thus they can be effectively removed

from the air by HEPA filters (99.97% efficient at 0.3 micrometers) in

respirators, vacuums and air filtration devices. It has been speculated that

the harsh mechanical action of blasting may break apart mold spores into

smaller particles, some of which are likely to be smaller than 0.3

micrometers. Since this kills the spore, there is no chance that it could

cause an infection. However, the primary health effects of mold are allergic

and perhaps toxic, not infectious. These effects are not reduced by being

broken into very small particles. If this speculation is correct, these

particles could pass right through HEPA filtration, potentially creating

exposure and cross-contamination issues. Similar problems could perhaps

arise when blasting is used to remove lead paint or other hazardous

contaminants.

Most common media types, such as sand, are overly aggressive for the

purposes mentioned above and cause unacceptable appearance or even

structural damage to wood surfaces. Almost all media types, such as sodium

bicarbonate ( " soda " ), leave a large amount of used media that must be

cleaned up, in addition to the removed contaminants.

Some media, such as plastic chips and sponges with embedded abrasives, are

designed to be recycled to make their use cost- effective. Recycling may be

feasible for fire restoration uses, but according to IICRC S520 recycling of

media used for mold remediation is not advisable, as it is not known whether

present methods of recycling are adequate to remove mold contaminants

effectively. So for mold remediation, these " recyclable " types of media

should only be used once, which usually makes them prohibitively expensive.

Yet another potential disadvantage of blasting is that concentrated air

pressure at the point of contact with the surface being cleaned has

significant potential to force air, media and entrained contaminants through

building penetrations into uncontaminated areas, even if the work area is

kept under negative pressure.

Most blasting methods require a considerable investment in equipment and a

significant amount of time to set up, which means that their use is a lot

less efficient on smaller jobs.

Safety precautions necessary with any blast method may include eye, face,

and respiratory protection. Most blast methods are very noisy, so hearing

protection must be used.

The two most widely used media for restoration and mold remediation are soda

and dry ice. We'll discuss these two individually.

Soda blasting is very effective at removing char, smoke residue and mold

growth from framing without causing excessive damage to the wood. This is

because the soda media is very soft. Unfortunately, soda blasting produces a

tremendous amount of very fine dust and leaves a lot of debris from the

expended media that can be difficult and time-consuming to clean up. It has

a fairly high production rate.

Dry ice blasting is certainly the most unusual of the blast media. It uses

pellets or shavings of dry ice (solid CO2) as a blast media, which

eliminates some of the disadvantages of other media.

Unlike other media, dry ice sublimates (goes from a solid to a gas without

passing through a liquid phase) on impacting the surface being cleaned. When

it goes from a solid to a gas, it tends to spread out across the surface of

the material which causes a " shearing "

effect that efficiently removes contaminants from the surface while causing

little if any surface damage. For certain types of contaminants, such as

oils and waxes, thermal shock also contributes to the cleaning effect. As

the blast media becomes a gas and dissipates, only the contaminants removed

from the surface are left to be cleaned up. Highly efficient removal of

contaminants, minimal surface damage and no media residue to clean up seem

to make dry ice blasting the ideal mold remediation method.

However, dry ice blasting has all the disadvantages of blasting in general,

with the exception of a media waste stream, and it has some very serious and

specific safety concerns. These can all be overcome, but you should plan

before using this cleaning method.

Dry ice blasting methods vary considerably. Some use prepared pellets, while

with others the machine generates its own pellets or flakes from blocks of

dry ice. Dry ice media is significantly more expensive than most others,

inherently inconvenient and potentially hazardous to handle. Some methods

have a much higher production rate than others. The amount of dry ice used

varies from as little as ¼ pound per minute to more than 10 pounds per

minute.

The surface temperature of dry ice is -110°F, more than adequate to cause

serious damage to human skin. Heavy gloves should always be worn when

handling dry ice or its containers. Use tongs when handling dry ice blocks.

CO2 gas is 1.56 times as heavy as air. Since it fills up a space from below,

it displaces oxygen and can potentially create a highly hazardous

reduced-oxygen atmosphere. High concentrations of CO2 gas also have direct

health effects, even if the oxygen level remains adequate. Containment may

limit ventilation enough that excessive levels of CO2 may build up. Keep in

mind that such a high-volume blast system adds a tremendous amount of air to

the space (as propellant), in addition to the CO2. To maintain appropriate

negative pressure differentials, you may have to significantly increase your

volume of exhaust air.

We attempted to find some information on CO2 levels that are typically

generated during dry ice blasting. We were unable to find any information

that would allow us to report exposure levels.

However, in small areas or confined spaces, especially one that is below

grade, such as a crawlspace, these issues could become critical.

The OSHA Permissible Exposure Limit (PEL) for CO2 gas is 5000 ppm

(0.5%) for an eight-hour time-weighted average; 40,000 ppm (4%) is the

Immediately Dangerous to Life and Health (IDLH) concentration.

Engineering controls, such as exhaust fans (HEPA filtered if the air being

exhausted is or may be contaminated) at ground level may be able to keep it

below these levels, if properly used.

Supplied-air or self-contained (SCBA) respirators must be used if

engineering controls do not keep levels below the PEL. Continuous monitoring

of CO2 levels, at least in confined spaces, is required to ensure worker

safety.

According to the Canadian Centre for Occupational Health and Safety,

" Exposure to 10% for 1.5 minutes has caused eye flickering, excitation and

increased muscle activity and twitching.

Concentrations greater than 10% have caused difficulty in breathing,

impaired hearing, nausea, vomiting, a strangling sensation, sweating, stupor

within several minutes and loss of consciousness within 15 minutes. Exposure

to 30% has quickly resulted in unconsciousness and convulsions. Several

deaths have been attributed to exposure to concentrations greater than 20%.

Effects of CO2 can become more pronounced upon physical exertion, such as

heavy work. "

Blast methods of cleaning are extremely versatile and potentially have many

uses in the restoration and remediation industries.

However, inherent characteristics can cause undesired side effects if not

adequately addressed.

FAIR USE NOTICE:

This site contains copyrighted material the use of which has not always been

specifically authorized by the copyright owner. We are making such material

available in our efforts to advance understanding of environmental,

political, human rights, economic, democracy, scientific, and social justice

issues, etc. We believe this constitutes a 'fair use' of any such

copyrighted material as provided for in section 107 of the US Copyright Law.

In accordance with Title 17 U.S.C. Section 107, the material on this site is

distributed without profit to those who have expressed a prior interest in

receiving the included information for research and educational purposes.

For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml.

If you wish to use copyrighted material from this site for purposes of your

own that go beyond 'fair use', you must obtain permission from the copyright

owner.

[Guest guest]

-----Original Message-----From: Moffett pmoffett@...

may have mentioned in the past that the ter "dry ice blasting" should be

changed to "dry ice treatment" I'll vote for that!!I shall start to use the term "specially applied sodium bicarbonate treatment" also.