36. Warnings in North America: what the same manufacturers do and do not say

Section 16 evaluates manufacturer and operator documents that describe the formation pathway. Most of them are European or are addressed to a European market. The question for this edition is what the same manufacturers say in their North American documents, since the Hazard Communication Standard places the reaction products of anticipated use on the manufacturer’s side of the line, and since the Canadian Hazardous Products Regulations require hazardous decomposition products to be stated. The following is the result of a search of publicly available sheets and bulletins; where a document could not be retrieved, that is recorded at the end of this section.

One manufacturer warns on the American market

Frenzelit publishes its TechInfo 28 in English as “Chromium(VI)-Formation at High Temperature”, version code V2-ABE-MSK/08.25, that is August 2025 and thus a revision of the German edition of January 2024. The document is cited in Section 16 and is publicly listed in the download area of the company’s international pages and of its United States region pages. It states that “When using chromium-alloyed steels, chromium(VI) compounds can form under certain conditions” and names the conditions that must all be met: “Presence of chromium-alloyed steels”, “Presence of alkali or alkaline earth metal oxides (especially calcium oxide)”, “Presence of oxygen (e.g., ambient air)” and “High temperatures (> 350 °C)”. As examples it names the use of calcium-containing lubricants for chrome-alloyed screw connections and the use of calcium oxide-containing materials for the thermal insulation of hot components. [15, 176]

The document also contains a sentence about the company’s own products: “Please note that Frenzelit insulation materials also contain calcium oxide in varying proportions.” As a consequence it requires that “In these cases, special safety precautions must be taken during dismantling, inspection, and other work” and that the disposal instructions for chromium(VI) compounds be observed. [176]

Three limits of this finding should be stated. The document is a translation of the German sheet, as its version code shows. It sits in the download area for gasket materials rather than with the insulation products. And it cites no American or Canadian rule, although the same company does publish a technical information sheet on California Proposition 65 in English, so the absence of a sheet written for the American legal position is not a question of language. [176]

What the other North American sheets state under decomposition products

Section 16 records the two Morgan sheets for Cerachrome, Z-Blok CR Grade and Ceraform 130, whose section 10 states “Hazardous decomposition products: None” and in which the word hexavalent does not occur [95, 77]. The further North American English sheets of the same manufacturer follow the same pattern: sheet 101 for the 1260 products, FireMaster Endowrap, Kaocrete and Kaolite, first issued 1 May 1987 and last revised 21 February 2022; sheet 156 for the Cerox castables and Valcor G; sheet 159 for Cerox 700; sheet 201 for the refractory ceramic fibre products Cerablanket, Kaowool, Cerwool, Pyro-Bloc and Premax; sheet 365 for Superwool XTRA; and sheet RP280 for the polycrystalline wool Alfibond A. None of them mentions chromium, chromate or hexavalent chromium, and none addresses contact with chromium-alloyed steel. The Canadian-format French sheet 378 for the Superwool papers states under “PRODUITS DE DECOMPOSITION” the binder products above 200 °C and nothing further. [177]

The company’s own datasheet for refractory ceramic fibre blanket, United States code 5-14-205 of February 2016, covers Kaowool, Cerablanket, Cerachem and Cerachrome and describes the last of these with the words “Cerachrome® Blanket is made from spun aluminasilica-chromia fiber”. The chromium content is thus declared as a constituent. Neither the datasheet nor the safety data sheets it cross-references says anything about what becomes of that constituent in service. [178]

The picture is the same at the other suppliers. The Alkegen sheet M0558A for Insulfrax 1300 HT, effective 15 May 2023, states “HAZARDOUS DECOMPOSITION PRODUCTS: None.”; the sheet M0055A for the Fiberfrax high purity papers, effective 15 December 2022, lists only binder smoke, carbon monoxide, carbon dioxide, nitrogen oxides and hydrocarbons. The Safe Use Instruction Sheet that ROCKWOOL issues for North America in place of product safety data sheets, version 2.2 of 14 April 2026, covering seven product families including ProRox, describes the material as “Chemically inert. Stable under normal conditions.” and limits decomposition to the binder products above 390 °F. The Promat sheets for PROMATECT H and for the Microtherm 1000R family state that no hazardous decomposition products are known. The Johns Manville sheet for calcium silicate pipe, block and board insulation, which covers Thermo-12 Gold and Thermo-1200, version 2.2 of 17 June 2019, lists no hazardous decomposition products at all and states “No decomposition if stored and applied as directed”. The 3M Canadian sheet for the Interam endothermic mats, version 3.00 of 26 June 2025, lists carbon monoxide and carbon dioxide. The CertainTeed sheet for mechanical and OEM glass wool of 2 November 2012 names oxides of carbon, sulfur, arsenic and nitrogen, hydrogen chloride, antimony, bromide gas, hydrogen bromide, formaldehyde and traces of hydrogen cyanide, and chromium is not among them. In none of these documents does chromium, chromate or hexavalent chromium occur. [179, 180, 182, 183, 185, 186]

The interface is addressed in North America, for a different question

The interface between insulation material and chromium-alloyed steel is not absent from the North American technical literature. Johns Manville publishes technical bulletin IND-TB009, “Stress Corrosion Cracking of Austenitic Stainless Steel”, dated 21 February 2020 and replacing an edition of 19 January 2018. The bulletin deals with insulation in contact with austenitic stainless steel, attributes the damage to chloride ions from wash-down water, brine, sea water, potable water, cleaning solutions and the insulation itself, and offers a corrosion inhibitor. The words chromium, chromate, hexavalent, calcium oxide, sodium oxide, alkali and alkaline do not appear in it. [184]

The same observation applies to the product data for the material. The ROCKWOOL data sheet for ProRox SL 960NA reports, as a test result under ASTM C795, “Stress Corrosion Cracking Tendency of Austenitic Stainless Steel = Passed”, with the chemistry of the test described in terms of chloride, fluoride and sodium. The property tested is the resistance of the metal. Section 12 of this analysis sets out why that is a different question from the formation of a hazardous substance at the same interface. [181]

The associations

The High Temperature Insulation Wool Coalition, whose health and safety pages list Morgan Thermal Ceramics, Alkegen, HarbisonWalker International and Nutec among its members, addresses fibre toxicology under the headings of dimension, durability and dose, a product stewardship program, respirator and handling guidance and California Proposition 65. It does not mention chromium, chromium(VI), chromate or any reaction with chromium-alloyed steel. For the North American Insulation Manufacturers Association and for the Thermal Insulation Association of Canada I have found no guidance on the subject. [187]

The European association does address it. The European Insulation Manufacturers Association published a position paper in January 2024, “Mineral Wool Products and Chromium(VI) Residues”, which states that “hexavalent chromium can be formed when stainless steel is exposed to high temperatures and humidity”, that “Stainless steel does not naturally contain hexavalent chromium”, and that “Mineral Wool insulation itself is not a source of chromium (including Cr(VI))”, adding of the alkali and alkaline earth content of the wool that “these elements are firmly integrated within the fibres glass network”. The paper gives no formation temperature, does not name calcium oxide, and contains no reference to North America, the United States, Canada or the Occupational Safety and Health Administration. [188]

The contrast is therefore not between a European awareness and an American ignorance of the subject. It is a difference in where the subject is addressed. In Europe an association has published a position on it, in the knowledge that a question exists. In North America the association that organises the same manufacturers has published nothing on it, while one of those manufacturers warns about it on the American market in its own technical information sheet.

Two North American documents that do describe the formation

A Californian air quality authority has had the process measured. The South Coast Air Quality Management District commissioned the College of Engineering Center for Environmental Research and Technology of the University of California, Riverside, to investigate hexavalent chromium emissions from industrial heat treating furnaces; the final report under contract 18258 is dated September 2021. Chromium(VI) was found to be emitted from an empty seasoned furnace, detectable from 1500 °F and highest at 2100 °F; the report states that the speciation depends on the availability of oxygen and of other alkali earth metals, discusses the chromium content of the refractory, and records the highest formation rates for fixtures of 304 and 310 stainless steel. No document of an insulation manufacturer is cited in it. [189]

The second document comes from the American trade press. A presentation by the power plant chemist David Addison, “Hexavalent Chromium Risks for Fossil and CCGT Plants”, revision 1.5 of 4 May 2021, prepared for a heat recovery steam generator training event and hosted by an American trade journal, states that “Calcium oxide is in some anti-seize pastes and also in most insulation/lagging materials” and that sodium is “normally present in insulation as well and will leach”, and recommends the use of calcium free insulation in contact with chromium containing liner plates in the hot end of the heat recovery steam generator, and the replacement of calcium oxide containing insulation in contact with chromium containing materials. It cites no manufacturer safety data sheet and no North American association guidance, and refers generally to safety notices issued by turbine manufacturers and by some plant owners and operators. [190]

To these should be added the document that stands at the beginning of Section 16. The product service bulletin PSB-43 of April 1990 and its edition PSB-43A of 1994 are documents of an American boiler manufacturer, addressed to American operators, and they describe the conversion of chromium compounds under alkaline and high-temperature conditions and the measures to be taken on removal. The earliest notice in this whole analysis is therefore a North American one, and it is thirty-six years old. [75]

What could not be retrieved

Four gaps belong in the record. One further Morgan North American sheet, number 367, could not be opened; nothing follows from that about its content. The resale portal of HarbisonWalker International returned empty documents, so I could not check whether the sentence that Section 16 records for the chrome-bearing refractory sheets also appears on that company’s insulation board and resale sheets. No product-specific North American safety data sheet for the ROCKWOOL ProRox range is publicly available; what exists for North America is the Safe Use Instruction Sheet named above. And the current North American industrial insulation sheets of Saint-Gobain and CertainTeed sit behind a product selector and were not retrieved, so the 2012 sheet cited here may not be the current one.

The absence of a statement in a document that could not be opened is not a finding. The absence of a statement in the documents that could be opened is one.