Nomex Gasket
Safety Information


What's This All About?
Many owners of ceramic charcoal cookers have replaced factory gaskets with various replacement gasket materials when the original gaskets fail. However, there have been concerns raised about the safety of using these other gaskets on ceramic charcoal cookers. Where did all the concern come from? Posters on ceramic charcoal cooker bulletin boards have posted that they were told, either by Rutland or by the manufacturer of their cooker, that the Rutland gasket is not safe for use around food. At various times, posters have indicated that Cotronics has said not to use their product, and then said it was alright to user their product. As result, there have been numerous arguments, sometimes heated, on these bulletin boards about the safety of using various non-original gasket materials on ceramic charcoal cookers. We have done our best to provide you with the information we have been able to accumulate on the subject in two previous articles about Rutland and Cotronics safety information, so you can make an informed decision as to whether or not you wish to use this product on your ceramic charcoal cooker.

In this third article in the series on gasket safety information, we take a look at Nomex, the material which is being used by at least one manufacturer of ceramic charcoal cookers for their gaskets. (See photo above right, courtesy of Fred's Music and BBQ.)


Disclaimer
We don't claim to know if it is safe or not for you to use a Nomex gasket product on your ceramic cooker. Any opinions stated here are just that, opinions. It is up to you to evaluate the information presented here and make your own decision as to whether or not you wish to use Nomex gasket material on your cooker.


What DuPont Has To Say
In order to try to better understand what might be the source of some of these claims, and to get an actual statement from the DuPont Corporation regarding the use of their product on a ceramic charcoal cooker, we contacted DuPont and asked for a letter stating their position. We informed DuPont that the letter would be published on our website. We received a very short response:

"We do not have an authorized statement for the use of Nomex® around food. Nomex® is not FDA approved."


We said it was short! Here is our interpretation of their statement:

  1. Since the product is not intended to be used around food, they have not conducted any testing related to the use of Nomex around food.

  2. No testing means no safety data, so they have no statement to make regarding the safety of using Nomex around food.

  3. Nomex is not FDA approved, which probably means you might not be able to use it in a commercial application, but we aren't talking about that.
Sounds pretty similar to what Rutland said, doesn't it? Notice that unlike Rutland, DuPont does not make the "we do not recommend it since we have no data" statement. So, where does this leave us? Since DuPont's brief statement didn't contain any information regarding the safety of using their product around food, we can look to some other sources of information. DuPont has published a Material Safety Data Sheet (MSDS) and a Technical Guide for their product.


Nomex Material Safety Data Sheet (MSDS)
In the Stability and Reactivity section of the MSDS, we find:

Decomposition : Decomposition temperature : > 300° C (> 572° F) Hazardous decomposition products Carbon monoxide, nitrogen oxides (NOx), Hydrogen cyanide (hydrocyanic acid).
So, apparently exposure to temperatures above 572° F can release Hydrogen Cyanide. This is certainly possible when using a ceramic charcoal cooker, but there is more information about this in the next section from the Information Guide.

Next in Section 11: Toxicological, we find a few interesting items. Nomex does not cause skin sensitization, is not carcinogenic, and is not a skin irritant. Also, except when processing the material, fibers are non-respirable. However, Nomex does contain some amounts of N,N-Dimethylacetamide (DMAC) and here we start to see some worrisome information:

Repeated dose toxicity:
Dermal -- Central nervous system depression, Liver effects, Skin effects
Oral -- Pathologic changes, Stomach, Testes, Liver, Kidney, Abnormal decrease in number of red blood cells
Inhalation -- Kidney effects, Liver effects, Retinal damage
We don't believe, however, that there can occur in use in a ceramic cooker sufficent exposure to DMAC to be of worry. From the Emergency Overview section we find:
The hazards of this product are associated mainly with its processing. Dust may form explosive mixture in air. High concentrations of dust can irritate eyes, nose and respiratory system and cause coughing and sneezing. Processing meta-aramid products can release Dimethyl Acetamide (DMAC). Hazards related to DMAC include: May be harmful by inhalation (after often repeated exposure). May be harmful in contact with skin (after often repeated exposure). Liver and kidney injuries may occur.

So, no food safety information, but also no indication that casual usage should be a problem either as the hazards outlined are primarily associated with processing Nomex, not using it. There is more information in the Nomex Technical Guide.


Nomex Technical Guide
The Technical Guide tends to put into plain English similar information to the technical information you find in the MSDS. Regarding the release of Hydrogen Cyanide, in Section 5: Toxicology of the Technical Guide we find:

When NOMEX® is subjected to flame or intense heat, it is converted to the usual combustion products for substances of the same elemental composition: carbon dioxide, water and oxides of nitrogen. However, carbon monoxide, small amounts of hydrogen cyanide and various other chemical residues (some possibly toxic or irritating) may be produced, depending on the conditions of burning. In small-scale evaluations, combustion products from NOMEX® appear to have similar toxicity as smoke from burning wood and other natural, combustible materials.
Regarding the presence of N,N-Dimethylacetamide we find:
The fiber contains up to 12% moisture (depending upon storage and use conditions) and a small amount of residual dimethylacetamide (DMAC) from the manufacturing process.
However, there is no further information beyond what the MSDS provided.


Exposure to UV Radiation
While not related to safety, we thought we would mention one other interesting property of Nomex. We hold a commercial pilot license for "Lighter Than Air, Free Balloon with airborn heater". In other words, we are a commercial hot air balloon pilot. Kevlar is sometimes used for the suspension cables used to connect the envelope to the basket in hot air balloons. These cables are protected from UV exposure by a heat-shrink tubing. We were instructed to carry electrical tape with us and if we ever melted the heat-shrink tubing that surrounded the Kevlar cable, we should wrap it as soon as possible with tape to protect the Kevlar from UV exposure. We were then to get the balloon to a repair station to replace the damaged heat-shrink tubing. Well, Nomex is a polymeric material like Kevlar and it suffers from the same degradation upon exposure to UV. From the Technical Guide:

"The absorption spectrum of Nomex overlaps with the energy spectrum produced by natural sunlight in the near-UV and lower visible regions. Nomex absorbs its maximum energy at the high end of the UV spectrum (approximately 360 nanometers), where the relative intensity of the UV component of most light sources is greatest.
To make a long story short, Nomex will lose approximately 50% of its mechanical strength with 80 hours of exposure to UV light. This doesn't sound like a problem for ceramic cookers, but it is something to consider as none of the other gasket materials we have examined suffer from this effect.


Conclusions
You should carefully read all of the information available before drawing your own conclusion about the safety of using this material on your ceramic charcoal cooker. This is what we conclude regarding Nomex:

  1. DuPont has made no data available as to the safety of using Nomex products around food.
  2. DuPont also does not say that such use is unsafe. In fact, they say nothing other than to point out that Nomex is not FDA approved.
  3. DuPont therefore also does not recommend against using Nomex in this application.
  4. The possibility of producing hydrogen cyanide is not a significant concern as burning wood will also produce hydrogen cyanide.
  5. The presence of N,N-dimethylacetamide doesn't appear to be a problem as the quantity present is low enough that significant quantities should not be released to produce the health hazards listed in the MSDS when using Nomex in a ceramic cooker.
So, it is our personal opinion that there is no significant level of risk associated with using the Nomex gasket in a ceramic charcoal cooker. But, as we have stated, you should evaluate the available information and draw your own conclusions.


References
Nomex Technical Guide
DuPont MSDS for Nomex Meta-Aramid


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