Hello
This is Dan from Vaporgenie.
We dont monitor this thread (or any other thread). We are happy to respond to questions, but we need to be alerted by email or through our website. So in the future dont hesitate to contact us via our website if you want us to respond.
So there were some questions about silicon carbide. The folks at Alivi8 stated the following:
"It has been brought to my attention that vaporgenie have been making posts
insinuating there may be health issues relating to the metal foam filters in the Alivi8,
having spoke with the manufacturers of the FeCrAlY filters I am assured
the material is perfectly safe for use in this particular application,
unfortunately it can not be said the same with this competitors Silicon Carbide filter,
when exposed to temps as low as 1200C Silicon carbide can produce SiO2 (silicon oxide)
Cristobalite which is a known CANCER CAUSING AGENT if ingested or inhaled.
the unique tortuous path design taken by the vapor in the Alivi8 enhances and cools
the vapors flavour and creates a sticky trap for any potential material passing through the system,
the same can not be said for the straight through designs of the Vaporgenie,
any loose particles will be inhaled and ingested."
Here are the facts:
Silicon carbide forms an extremely thin, adherent silicon dioxide (SiO2, silica) layer when heated. This is called a "passivation" layer because it protects the underlying material. Silicon dioxide is the main component of borosilicate glass (pyrex). This silica layer is sticks to the silicon carbide and does not produce particles.
Silicon carbide is typically rated for continuous use in air up to about 1650C. This means that at temperatures below 1650C, the rate of oxidation is essentially zero after the passivation layer is formed. I dont know where the 1200C figure came from, but I assume that this is the temperature at which the silica passivation layer is first formed. But this does not mean that silicon carbide will form silica particles at 1200C. It just means that this is the temperature at which the oxide passivation layer first forms.
Silica dust, like virtually any other type of fine dust, is harmful to the lungs. It can cause silicosis: http://en.wikipedia.org/wiki/Silicosis Silicosis is an occupational illness caused by working in very dusty environments. One must inhale significant amounts of silica dust to cause silicosis.
The VaporGenie silicon carbide filter will not produce silica particles or any other type of particles and so cannot possibly cause silicosis or produce any other particles.
The "christobalite" referred to by Alivi8 is a particular type of silica. http://en.wikipedia.org/wiki/Silica I dont see any reason to assume that the passivation layer formed on silicon carbide is "christobalite", and even if it was, it is extremely thin and strongly adherent to the silicon carbide. There is no reason to be concerned about the silica passivation layer on silicon carbide any more than being concerned about ordinary glass or borosilicate glass.
Inhaling virtually any type of ceramic powder or dust material is harmful to the lungs. That is why the silicon carbide filter in the VaporGenie is made of monolithic silicon carbide created by chemical vapor deposition. Other, cheaper ceramics are typically made by sintering ceramic particles. These ceramic materials present a hazard of particle inhalation because the ceramic particles can break off. This does not happen with the monolithic silicon carbide in the VaporGenie. The VaporGenie ceramic filter is not made of sintered particles for this reason.
Also, the SIZE of the particles is very important. The smaller the particles, the more harmful they are to the lungs. The most dangerous particles are sub-micron size. Thats because these small particles are not collected by upper air passages in the lungs, but instead they go all the way into the tiny chambers of the lungs where air exchange occurs. So, large, dust-like particles are not dangerous (they are easily filtered out by the lungs), but microscopic, sub-micron particles are dangerous. Very fine submicron particles are difficult to filter from air. If the FeCrAl filter is creating these fine particles, they absolutely will NOT be removed by the serpentine path used in the Alivi8.
The particular silicon carbide used in the VaporGenie filter is rated for use in air up to 1650C. A butane lighter cannot even come close to this temperature (e.g. 1200-1300C absolute max). A butane lighter cannot heat the ceramic to 1200C because the silicon carbide has a high thermal conductivity and the foam filaments are relatively thick. The FeCrAl material, by comparison, has very thin filaments, which are much more easily heated to the full temperature of the lighter flame.
FeCrAl alloys, by comparison, are rated for use in air up to 950-1400C. http://www.alloysino.com/FeCrAl_resistance_heating_alloy.html Only the more exotic alloys (containing niobium or molybdenum) can go to 1300 or 1400 C. The FeCrAl alloys can experience oxidation fast enough to degrade the material at temperatures as low s 950C. I have no idea what type of alloy the Alivi8 uses. If the folks at Alivi8 want to continue this discussion, they should indicate precisely which alloy they are using and indicate its maximum continuous use temperature.
Typically what happens with metals above the max use temperature is that the metal is consumed and particles are produced. Particles are produced because the metal oxides formed are not adherent. This is what happens for example when a light bulb filament is exposed to air. The metal burns up into a puff of metal oxide particle smoke.
What I personally experienced with the FeCrAl materials was a worrisome level of oxidation and metal fume production. This is one of the reasons why we chose not to use them. I do not recall the exact alloy I experimented with. It could have been one of the FeCrAl alloys with a max temp rating of only 950C. The Alivi8 might use a better allot for all I know.
What has happened here is that the folks at Alivi8 have fished around for something scary to say about silicon carbide. They didnt find anything worth worrying about. Silicon carbide is extremely heat resistant and chemically stable. It does not produce particles when heated. It slowly forms a very stable and adherent passivation layer of silicon dioxide on its surface when heated.
One more thing: SURFACE OXIDE PASSIVATION LAYERS ARE VISIBLE. If they are thick enough, they can be seen with the unaided eye, on metals OR silicon carbide. They appear as sheen-like color variations or rainbow colors. When oxidation occurs, the colors will shift around and change. I have personally observed these colors changing and shifting around on the Alivi8 filter, which of course indicates a significant level of oxidation and chemical reaction of the metal. By comparison, no such colors will be formed on silicon carbide by the same butane flame. The silicon carbide is much more stable and resistant to oxidation than FeCrAl alloys.
There IS an issue worth worrying about regarding lighters: the dust produced by flint lighters. The lighter flint material is made of misch metal, a mixture of rare earth elements (lanthanum, cerium, neodymium etc). When you strike a flint lighter, the misch metal is burned, producing very fine inhalable particles (i expect they are sub-micron in view of their blue-ish, smoke-like appearance). As I noted above, fine particles are hazardous. Also, the misch metals are chemically toxic. So its sort of a double-whammy. There is an interesting downloadable scientific paper about the pulmonary toxicity of rare earth metals on our website:
http://www.vaporgenie.com/component/option,com_fjrelated/Itemid,35/id,80/layout,blog/view,fjrelated/
Here is the paper:
https://www.vaporgenie.com/images/flint_dust.pdf
This is Dan from Vaporgenie.
We dont monitor this thread (or any other thread). We are happy to respond to questions, but we need to be alerted by email or through our website. So in the future dont hesitate to contact us via our website if you want us to respond.
So there were some questions about silicon carbide. The folks at Alivi8 stated the following:
"It has been brought to my attention that vaporgenie have been making posts
insinuating there may be health issues relating to the metal foam filters in the Alivi8,
having spoke with the manufacturers of the FeCrAlY filters I am assured
the material is perfectly safe for use in this particular application,
unfortunately it can not be said the same with this competitors Silicon Carbide filter,
when exposed to temps as low as 1200C Silicon carbide can produce SiO2 (silicon oxide)
Cristobalite which is a known CANCER CAUSING AGENT if ingested or inhaled.
the unique tortuous path design taken by the vapor in the Alivi8 enhances and cools
the vapors flavour and creates a sticky trap for any potential material passing through the system,
the same can not be said for the straight through designs of the Vaporgenie,
any loose particles will be inhaled and ingested."
Here are the facts:
Silicon carbide forms an extremely thin, adherent silicon dioxide (SiO2, silica) layer when heated. This is called a "passivation" layer because it protects the underlying material. Silicon dioxide is the main component of borosilicate glass (pyrex). This silica layer is sticks to the silicon carbide and does not produce particles.
Silicon carbide is typically rated for continuous use in air up to about 1650C. This means that at temperatures below 1650C, the rate of oxidation is essentially zero after the passivation layer is formed. I dont know where the 1200C figure came from, but I assume that this is the temperature at which the silica passivation layer is first formed. But this does not mean that silicon carbide will form silica particles at 1200C. It just means that this is the temperature at which the oxide passivation layer first forms.
Silica dust, like virtually any other type of fine dust, is harmful to the lungs. It can cause silicosis: http://en.wikipedia.org/wiki/Silicosis Silicosis is an occupational illness caused by working in very dusty environments. One must inhale significant amounts of silica dust to cause silicosis.
The VaporGenie silicon carbide filter will not produce silica particles or any other type of particles and so cannot possibly cause silicosis or produce any other particles.
The "christobalite" referred to by Alivi8 is a particular type of silica. http://en.wikipedia.org/wiki/Silica I dont see any reason to assume that the passivation layer formed on silicon carbide is "christobalite", and even if it was, it is extremely thin and strongly adherent to the silicon carbide. There is no reason to be concerned about the silica passivation layer on silicon carbide any more than being concerned about ordinary glass or borosilicate glass.
Inhaling virtually any type of ceramic powder or dust material is harmful to the lungs. That is why the silicon carbide filter in the VaporGenie is made of monolithic silicon carbide created by chemical vapor deposition. Other, cheaper ceramics are typically made by sintering ceramic particles. These ceramic materials present a hazard of particle inhalation because the ceramic particles can break off. This does not happen with the monolithic silicon carbide in the VaporGenie. The VaporGenie ceramic filter is not made of sintered particles for this reason.
Also, the SIZE of the particles is very important. The smaller the particles, the more harmful they are to the lungs. The most dangerous particles are sub-micron size. Thats because these small particles are not collected by upper air passages in the lungs, but instead they go all the way into the tiny chambers of the lungs where air exchange occurs. So, large, dust-like particles are not dangerous (they are easily filtered out by the lungs), but microscopic, sub-micron particles are dangerous. Very fine submicron particles are difficult to filter from air. If the FeCrAl filter is creating these fine particles, they absolutely will NOT be removed by the serpentine path used in the Alivi8.
The particular silicon carbide used in the VaporGenie filter is rated for use in air up to 1650C. A butane lighter cannot even come close to this temperature (e.g. 1200-1300C absolute max). A butane lighter cannot heat the ceramic to 1200C because the silicon carbide has a high thermal conductivity and the foam filaments are relatively thick. The FeCrAl material, by comparison, has very thin filaments, which are much more easily heated to the full temperature of the lighter flame.
FeCrAl alloys, by comparison, are rated for use in air up to 950-1400C. http://www.alloysino.com/FeCrAl_resistance_heating_alloy.html Only the more exotic alloys (containing niobium or molybdenum) can go to 1300 or 1400 C. The FeCrAl alloys can experience oxidation fast enough to degrade the material at temperatures as low s 950C. I have no idea what type of alloy the Alivi8 uses. If the folks at Alivi8 want to continue this discussion, they should indicate precisely which alloy they are using and indicate its maximum continuous use temperature.
Typically what happens with metals above the max use temperature is that the metal is consumed and particles are produced. Particles are produced because the metal oxides formed are not adherent. This is what happens for example when a light bulb filament is exposed to air. The metal burns up into a puff of metal oxide particle smoke.
What I personally experienced with the FeCrAl materials was a worrisome level of oxidation and metal fume production. This is one of the reasons why we chose not to use them. I do not recall the exact alloy I experimented with. It could have been one of the FeCrAl alloys with a max temp rating of only 950C. The Alivi8 might use a better allot for all I know.
What has happened here is that the folks at Alivi8 have fished around for something scary to say about silicon carbide. They didnt find anything worth worrying about. Silicon carbide is extremely heat resistant and chemically stable. It does not produce particles when heated. It slowly forms a very stable and adherent passivation layer of silicon dioxide on its surface when heated.
One more thing: SURFACE OXIDE PASSIVATION LAYERS ARE VISIBLE. If they are thick enough, they can be seen with the unaided eye, on metals OR silicon carbide. They appear as sheen-like color variations or rainbow colors. When oxidation occurs, the colors will shift around and change. I have personally observed these colors changing and shifting around on the Alivi8 filter, which of course indicates a significant level of oxidation and chemical reaction of the metal. By comparison, no such colors will be formed on silicon carbide by the same butane flame. The silicon carbide is much more stable and resistant to oxidation than FeCrAl alloys.
There IS an issue worth worrying about regarding lighters: the dust produced by flint lighters. The lighter flint material is made of misch metal, a mixture of rare earth elements (lanthanum, cerium, neodymium etc). When you strike a flint lighter, the misch metal is burned, producing very fine inhalable particles (i expect they are sub-micron in view of their blue-ish, smoke-like appearance). As I noted above, fine particles are hazardous. Also, the misch metals are chemically toxic. So its sort of a double-whammy. There is an interesting downloadable scientific paper about the pulmonary toxicity of rare earth metals on our website:
http://www.vaporgenie.com/component/option,com_fjrelated/Itemid,35/id,80/layout,blog/view,fjrelated/
Here is the paper:
https://www.vaporgenie.com/images/flint_dust.pdf
