6.0) FIRE and SMOKE: (page 2 of 6)

6.13.h) Steel and Metal Compliance: Structural steel and metal building components shall meet the minimum structural requirements as described in the  International Building Code or the NFPA 5000 Building Construction & Safety Code after they have been mitigated or restored.

Steel decks or formed steel after mitigation or restoration procedures shall meet the minimum paint, enamel or other approved protection requirements described in national and local adopted building codes, or industry accepted standards.

6.14) Surfaces Conditions: Surfaces should be pre-inspected before proceeding with the mitigation or neutralizing of the surface.  The inspection of surfaces should include both pre-existing conditions and post-fire conditions.

The pre-existing condition of components and contents could be controversial at times, and all pre-existing conditions should be noted in writing and photographed.

6.14.a) Post-Fire Conditions: Post-fire damages to components and contents would be caused by smoke, soot, heat and moisture.  Secondary damages would be mold (fungi) and corrosion (rust).

6.14.b) Pre-Existing Conditions: Pre-existing condition to components and contents would be scratches, dents and tears, as well as normal wear and usage. 

6.15) Carbon Dioxide: Organic materials such as; wood, coal, oil, lime, foods and inorganic materials such as; nylon, plastics, etc. contain hydrocarbons.  The combustion by-product of hydrocarbons is carbon dioxide that dissolves in water to form carbonic acid. Carbonic acid is considered moderately corrosive.

When carbonic acid is present, the neutralization process of vulnerable materials should commence immediately.  Carbonic acids although not as corrosive as hydrochloric acid, will accelerate the oxidation of metals prematurely through reduction.

6.16) Polyvinyl Chloride (PVC):  Polyvinyl chloride (PVC) is used extensively in the manufacturing of building components and contents as described in Section 6.16.a.

The by-product of decomposed PVC is hydrogen chloride (HCl) and readily dissolves in water through a process called hydrolysis to form hydrochloric acid with the same formula (HCl).  HCl creates a highly corrosive reaction with metals and starts deteriorating the metal surface on impact.  Lead gases and soot could be produced when PVC products contain lead as a stabilizer as described in Section 6.16.b.

Hydrogen chloride gases react with metals to stimulate corrosion when the metal temperature drops below the acid dew point of the gas, causing hot acidic condensates to form, which are highly corrosive to carbon steels.  The thermal expansion of metals can allow vapors of hydrogen chloride gases to penetrate the outer layer of the protective coating, and the metal itself.  The effects of PVC on metal surfaces is not readably noticeable and can take up to 2 to 4 weeks before oxidation/corrosion is visible.

Stainless steel is vulnerable to hydrogen chloride as described in Section 6.17.b. 

Photo 6-16-A shows indirect heat and hydrochloric acid damages on a corrugated metal roof deck coated with an iron oxide primer.  The photo in 6-16-B shows atmospheric heat and hydrochloric acid damage on a corrugated metal roof deck coated with a silico-chromate primer.  Both metal roof decks were located within the same facility, where the fuel source contained PVC building components, PVC contents, nylon clothing and nylon carpet. 

Photo 6-16-A
Iron Oxide Coated Metal Deck
Source: William Yobe & Associates

Photo 6-16-B
Silico-Chromate Coated Metal Deck
Source: William Yobe & Associates

Note: The silico-chromate coated metal deck shown in Photo 6-16-B although rusting is not as deteriorated due to less heat and the chromium alloy found in silico-chromate primers, which offers moderate corrosion protection.  The period (time frame) of the corrosion shown in Photos 6-16-A and 6-16-B was four weeks after a fire.

Photo 6-16-C shows hydrochloric acid and carbonic acid damages on heavy machinery 15 days after an industrial fire, and the photo in 6-16-D shows steel stock that had a coating of factory applied oil that started to show rust formation in 7 days.

Photo 6-16-C
High Alloy Machinery
Source: William Yobe & Associates

Photo 6-16-D
Corroded Steel Stock
Source: William Yobe & Associates

When hydrogen chloride and water are present, the neutralization of the affected surfaces should commence immediately.

Hydrogen chloride resins and gases are corrosive and toxic, and could be present for days after a fire.  

When PVC is a known fuel source, metal surfaces should be neutralized and receive a protective coating of petroleum jelly, vegetable oil or equal to protect the surface from acid off-gassing.

Tarry Soot Formation (PVC)
Source: William Yobe & Associates
Photo 6-17-C

6.16.a) Components Containing PVC: PVC is used in the manufacturing of a large spectrum of building components and content furnishings.  The building construction industry is the second largest consumer of polymerized plastics.

Listed below are some items that can contain PVC:

Electrical: Wire insulation, conduit and fittings, J-boxes and device boxes, circuit breakers, receptacles, switches, light fixtures, etc.

Plumbing: Pipe and fittings, valves, pumps, faucets, supply lines, bath tub, shower enclosures, etc.

Flooring:  Vinyl base board, stair treads, tile (VCT), inlaid and one piece vinyl, nylon carpet, etc.

Appliances: Refrigerators (both in and out), dish washer, cloths washer, dryer, etc.

Building components: Windows, doors, cabinets, shelving, casing and baseboard, siding, shutters, mail boxes, wall accessories, wallboards, insulation, etc.

Contents: Chairs, tables, place settings, cups and plates, sporting goods, toys, stereos, computers and paraffin wax products, etc.  Clothing, such as nylons, polyester, etc.

6.16.b) Lead and Cadmium in PVC: Although not used in all products made from PVC, some PVC products are made with lead and cadmium as a stabilizing additive, which are labeled as hazardous substances per the ATSDR and the EPA.

Other stabilizers used in the manufacturing of PVC components are barium, calcium, zinc and tin, while cadmium is not commonly used today.

PVC's, when stable do not produce any known toxic substances and should not present a health threat.

The decomposition of PVC during a fire could possibly emit lead or cadmium by-products within the smoke and soot, which could be distributed throughout a structure and onto its contents.

Since the determination of whether decomposed PVC’s contain lead or cadmium is not noticeable, items such as; children's toys, silverware, flatware and glassware should be tested for lead and cadmium, and properly neutralized or disposed.

6.17) Mitigation Procedures, When Carbon Dioxide and/or PVC is a Known Fuel Source: When carbon dioxide or polyvinyl chloride (PVC) is a known fuel source, the testing, confirmation and neutralizing of susceptible metal structural components and metal contents should commence immediately.

Combustion will produce three states of matter: solid, liquid and gases.  Since smoke colors can be white, gray, brown or black, their color should not be used as an indication of the soot’s acidic nature.

Mitigation should include, but not be limited to the following:

    Structural Components:
    - Door and cabinet hardware, hinges, knobs and pulls
    - Plumbing faucets, trim, valves, and supply lines
    - Bath tubs and shower surrounds
    - Bathroom and kitchen wall accessories, chrome or brass
    - Built-in appliances, chrome, painted surfaces,
       electrical motors, etc.
    - Light fixtures, ceiling and wall
    - Electrical device plates, (switch & receptacle) brass,
       chrome, steel, porcelain, etc.
    - Electrical service panel
    - Hot water tank
    - HVAC systems (furnace. A/C, etc.)
    - Glass, windows, doors, etc.
    - Structural steel, I-beams, tele-posts, etc.

    Contents:
    - Exposed glass, porcelain, mirrors, etc.
    - Metal picture frames
    - Brass items, beds, lamps, candle holders, etc.
    - Hard furniture, drawer pulls, hinges, etc.
    - Upholstery, should be vacuumed and dry sponged.
       If the soot has a tarry substance, dry sponging
       should be avoided

6.17.a) Metals: Ferrous and non-ferrous metals are affected by hydrogen chloride and hydrochloric acid, and would include stainless steel and galvanized metals.

Extracted from the Loss Recovery Guide with Standards (LRGS)

Find It Fast - With The ... LRGS - Navigational Index

6.17.b) Ferrous Metals: Ferrous metals are carbon, alloy, stainless and consist mainly of iron. 

Alloy and stainless steels contain additives such as; aluminum, chromium, copper, nickel, zinc, etc. that increases the corrosion resistance of metals.  Silicon is added to metal to increase strength, while the corrosion resistance of steel increases when its chromium content is 12% or higher. 

Hydrogen chloride gases will accelerate corrosion when the temperature of the hydrogen gases reaches 500º F to 1000º F and increases considerably when its temperature reaches 1200º F. 

Photos 6-17-A and Photo 6-17-B represent a metal roof deck impacted with hydrogen chloride gases that were over 2000º F per the fire report. Photo 6-17-A shows the metal roof deck after it was cleaned with a 13 pH detergent, using an abrasive cleaning sponge. Photo 6-17-B represents the same metal roof deck 6 months later.

Corroded Metal Deck after 13 pH Degreaser Cleaning
Source: William Yobe & Associates
Photo 6-17-A

Metal Deck in Figure 6-17-A
6 Months after Cleaning With a 13 pH Degreaser
Source: William Yobe & Associates
Photo 6-17-B

Note: The powdered rust formation confirms the persistent corrosion reaction of hydrochloric acid after using a high pH detergent.  This confirms the need of an ionic based chemical or vigorous agitation to un-align the formation of the metals’ molecules to their pre-right angles. 

Stainless steel is vulnerable to chlorides through the breakdown of the steels’ passive film causing staining and pitting.  Galvanized (zinc) coated steel, although non-corrosive, will breakdown through hydrolysis and rust when wet/moist for a considerable amount of time when exposed to hydrochloric acid.

When removing fire residues from metal surfaces, the pre-solvent-mechanical removal procedures described in the NIDR Guidelines for Fire and Smoke Damage Repair could apply.  The NIDR Guidelines also state the mechanical removal of fire residues does not guarantee neutralization or removal of acids, which may require additional treatments. The recommended NIDR mechanical removal techniques are outlined in Table 6-B.
 

Some Techniques for Mechanical Removal of Residues
© ASCR Reprinted with the permission of the
Association of Specialists in Cleaning and Restoration
Millersville, MD
Table 6-B
 

6.17.c) Non-Ferrous Metals: Non-ferrous metals such as; aluminum, copper and zinc are non-corrosive. 

Aluminum is resistant to corrosion through the oxide film that forms on its surface.  When hydrogen chloride gases impact aluminum, the white oxidation that forms on the surface of the metal could produce benzene (C₆H₆).

Copper is mined ore and is resistant to corrosion.  Moisture and oxygen will turn copper from red/orange to red/brown.  Copper, when exposed for long periods will produce a green film called patina, hydrogen containing chlorides will accelerate copper to the patina stage. 

Brass is an alloy containing copper and zinc.  High tensile strength brass contains small amounts of iron, magnesium, aluminum, lead and tin.  Naval brass contains more than 1% tin and is highly resistant to sulfur corrosion. 

6.17.d) Small to Medium Metal Surface Mitigation, When PVC is a Known Fuel Source: Building components such as; door hardware, metal doors, plumbing fixtures, electrical panels, light fixtures, furnace, hot water tank, etc. should be neutralized with an ionic cleaner.  Then all cleaning media should be rinsed with clean mineral free water and a coating of petroleum jelly, vegetable oil or equal should be applied if corrosive off gases are present.

When tarry soot is present, degreasers could be required. 

6.17.e) Large Metal Surface Mitigation, When PVC is a Known Fuel Source:  Several factors enhance oxidation and corrosion on metal surfaces after fire and smoke losses when PVC is the fuel source, those factors being; temperature, thermal expansion, alloying, moisture and oxygen.

Corrosion caused from the reaction of hydrochloric acid (HCl), unlike normal rusting does not stop when the moisture or oxygen source has been corrected.  Corrosion when produced from HCl rearranges the molecule make-up of the metal, and is irresolvable in some instances unless treated with the correct chemical or process. 

An example of repeated corrosion due to hydrochloric acid is shown in Photo 6-17-C and Photo 6-17-D.

Repeated Corrosion Due to PVC
Source:  William Yobe & Associates
Photo 6-17-D

Note: the corrosion bled through the tarry soot in Photo 6-17-D after it cured, while Photo 6-17-C was taken 6 months before Photo 6-17-D. The powdered rust formation on corroded steel is crystallization from salt.  For acids contain the ester of salt and the orange color is the result of the pigmentation of the iron.

The mitigation of large metal surfaces such as; metal roof decks, trusses, I-Beams, etc. would result in a complete restoration of the surface if neutralized before corrosion sets in. 

When neutralizing large metal surfaces before corrosion has started, the methods used should reduce the acid content of the metal to the minimum standards set-forth in SSPC-SP 12/NACE No.5 as outlined in Table 6-C.
 

  Contaminate Reduction Levels
Source: SSPC & NACE
Table 6-C

After a metal surface has been restored of its over-voltage, the metal surface should receive a coating of primer or paint to prevent normal electrochemical corrosion (rusting). Large metal surfaces can be mitigated or restored using (CO₂) dry ice blasting, soda ash blasting, pressure washing, high-pressure washing or blast-cleaning.

Pressure washing: Ionic cleaners and detergents can be applied with a pressure washer to neutralize hydrogen chloride or hydrochloric acid.  Basic residential pressure washers produce 2.0 to 5.0 gallons per minute and after pressure washing, airmovers and dehumidifiers could be required to prevent secondary damages such as microbiological growth, nominal electrochemical corrosion and flash rusting. 

When metal surfaces have accelerated rust due to HCl, commercial grade pressure washers that produce 4 to 14 gallons per minute would be required per the Steel Structures Painting Council (SSPC).

Excessive runoff water should be collected and disposed per EPA and state regulations. Surfaces receiving ionic cleaners should be rinsed with clean mineral free water.

C0₂: Dry ice blasting is an acceptable means of removing hydrogen chloride or hydrochloric acid before oxidation and corrosion is present.  Cold jet blasting / cleaning systems, the application machine used to force pellets through a regulated nozzle are capable of cleaning or blasting a surface.  This application system meets EPA, USDA and FDA guidelines since the dry ice pellets instantly vaporize without generating secondary waste.

Manufacturers of dry ice blasting systems state their systems will not effectively remove items such as heat treat scale, mill scale and scale corrosion.  Although dry ice blasting systems will remove soot, toxic residues, mold and biofilm buildups such as; listeria and salmonella, and is safe to use in the food, automotive and nuclear industries

Soda: Soda (baking) ash can be used to remove hydrogen chloride and hydrochloric acid before oxidation / corrosion is present, as well as after oxidation/corrosion has started. This is possible based on the varying abrasives available.  Plain soda ash when used with micro blasting systems could be used on fragile electronics, while soda ash containing heavy grit will remove rust and paints from steel substrates.  This application meets EPA, USDA and FDA guidelines since soda ash is a non-toxic organic food source.  Soda ash is applied dry or wet.  Wet applications could require a second application of clean mineral free water to remove soda ash residue.  Based on the type and condition of the surface being blasted, media waste should be cleaned-up and disposed accordingly. Baghouse type structures could be utilized with airmovers to catch soda ash media waste.

Blast-cleaning: Metal surfaces that have repeated corrosion due to HCl and have set for an amount time could require pressure washing with an ionic-cleaner, then blast-cleaning.  The degree of the corroded surface, intended surface results and the intended coating would determine which media and applicator would be appropriate. 

Blasting media such as sand, steel, iron, etc. are available in varying grits and applied via compressed air or rotary-type blasting equipment.  Both offer varying surface preparation through the type, shape and size of the media, as well as the speeds they are applied.

The following blasting surface degrees are available:

White metal clean: Is when no visible residues remain after blasting, and the surface has a uniformed color.
Near white clean: Is when traces of residues and mill scale is present after blasting.
Brush-off clean: Is the removal of loose residues.

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