# Cabot Microelectronics — Hazardous Materials Safety Interpretation **Citation:** 09-0067 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2009-07-20 09-0067 response to Cabot Microelectronics concerning 173.24. ## Document text <<>> U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration 1200 New Jersey Ave, S.E. Washington, D.C. 20590 JUL 2 0 2009 Mr. Michael Trembley Cabot Microelectronics 870 N. Commons Drive Aurora, IL 60504 Ref. No. 09-0067 Dear Mr. Trembley: This responds to your March 19,2009 letter requesting clarification of requirements in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171- 180) applicable to intermediate bulk containers (IBCs). Specifically, you ask if it is permissible to use vented caps to prevent hydrogen gas build up in an IBC to meet the provisions concerning venting in 9 173.24(g)(2). According to your letter, you plan to use a vented cap (e.g., G2 Plug Silicone Vent #48 1645 or equivalent) on an IBC containing a non-hazardous, water-based product to prevent the build up of hydrogen in the head space of the container. You state that hydrogen levels in excess of the 4% Lower Explosive Limit (LEL) concentration can build up over time inside a closed container such as an IBC and suggest that the use of a vented cap would prevent this from occurring. The answer is yes. It is the opinion of this Office that the use of a vented cap as described above to prevent hydrogen gas build up in the IBC is permissible, and does not constitute a design change that would necessitate retesting of the IBC. Please note that any change to the originally produced packaging involving structural design, size, material of construction, wall thickness, or manner of construction would constitute a design change that would require completion of the tests set forth in Subpart 0 of Part 178 of the HMR. I hope this answers your inquiry. Sincerely fl;d <<>> Headquanew 870 N. Cwnmm f)aive Aurora, It 6WM 630 375-@?i3 1 806.&1,2756 63ii 375,5539 fax W-CaWtomp wrn Mar& lfP,ZFIE)!2 G.5, Uepanmmt af Tmnspuftati~n Piyrlise and Nazlrrr%ous Mnteriab &fe't.ty Adnairt (3"l.tJ"i- 10) Office of Hwmdozzs M ~ M B I s %fety 1200 New Ja4sey Avenue, SF: Fast B~kitding. .2& Flcror Washington, BC' 20590 Attn: Mt. Edward 3: R4anulfa, i3ireeior Ot'tice of Hwrdeus h 5 c ~ i d 8 S~andwds Subject: ;Inre"rl.neiadon Requeajt for 49 CFR 1 T,1.24(g)(2) Dear Mr. k m l i o . PutsuaM to sn informal &lephrme c~nfauroe call eonducked m March 1 1.2009 befw een Roy Marshall. on behalf of C~bot Mirroelecaonics C2xparaapaa. and Sharu Kellry. we f a m l l y rqued y ~ u r tisistBRw 0t1 ri shippja&:mttfcrmlaked to the use of vented caps. SpeciRoslly. \ate would like to know i r i l i ~ -5ssibJe to usc a vented cap (eg. (i2 Plug Silicone Vent $481 645 pa equivaimtt) on u packgin& fa.&. an X~tem~ediillc BuLk Con~aiwr) co~~truninp a na- hWwdot.k, xvhh-ksed preduot to preyent ibe.buil6up of hwogen m the head @ace of the container if the venrpd ilydmp 8s Reaper reach %he L o w e Gxplabive Lh13r (LEL) of s 4% eoncmmtion with Bir iif the mqOfl ve~clr" ar fright onntairinq. Q ~ e ~ d y . hydrf>gea levels in m c e s of tk 4% LEL concentntion a t buildvp over ume inside a cJosed eonsner aoch sr an %mediate Bulk Canfaher. The use of a m t e d cap would prevent the buijujld-up ofh$fdr~gcn ursfde such a untUnerthus preventing the 4% LEL conccnmtion $om king reitch&. While (he initis! guidance we ncceiMd fmm the US. DFp-ent gf Tranqonatim seems fay-ic (i*. a v&ed csp would be pcmirrible unda &q circumstnnrcs described in L e second paragritph above). we respectfully requen a forms1 wriqefi inteqreration ofthe Wssibilixy of wnrrd caps (as discussed in pmgraph Ea.~.ab%~e) in sc~brdanee with 49 CFR 17?.24(g)(2). h addition. we have iti~luded a fopy ofthe-ini~ial inform~tion provided u, the L1.S. ~epsrtmenr of Transpoetion nnd cxsmplcr afrhc lntmnediatr Bulk Container ventilstion system oaps under carasidwTi:on. 'Kank pa^ fir p t t r blp in this matter. Sbcerely, Te1- 630.375.5576 Fax- 630.375.2082 Email- rnichag3-rrcmb*iry@c~k~tc'1*1tp~~:om <<>> HydrogenPackaging Issue We need help to determine what our options are in terms of eliminating the headspace build-up, proper classification, interactions with the DOT, any exemption opportunities, etc. Assuming the containers are hazardous, we need to be able to ship by ground and water. Air is not required, but if possible would be nice to have. Our internal policy is to ship Cargo Aircraft only. No passenger aircraft even if legally allowed. Packaging specs: We typically use 5-gallon plastic jerricans (3H1), 55 gallon drums (1H1) or tote (3 1HAI) ........................................................................... We have a product that is non-hazardous. This is a water-based product that is not flammable, corrosive, oxidizing, etc. Essentially it is used as part of a wire saw process to cut silicon ingots into thin wafers. As a result of this process, small bits of the silicon mix with the product. This material is re-used a number of times until the product becomes 'saturated' with enough silicon that it no longer can effectively cut the ingots via the wire saw process. This spent material is collected as it has the potential to be recycled and re-used. This material is also water based, not flammable, corrosive, oxidizing, etc. and is considered in itself non- hazardous. However, there is a reaction occurring between the silicon particles and the water. The silicon reacts with the water to form silicon dioxide and hydrogen gas. The hydrogen gas accumulates over time in the headspace of the containers- drums, jerricans and IBC type totes. The levels of concentration of H2 measure in the closed containers varies based on time, headspace volume and amount of silicon present in this spent material, and have been measured from 34%-75%. Once the cap is removed from the container, the H2 disperses quickly to atmosphere to levels below the LEL. Some initial measurements on drums that were initially stored using vented caps and then re-sealed for subsequent measurements: Drum 1 Drum 2 Drum 3 3 Slurry Height in /Immediate Drum :Hydrogen Very Full 34% 2" from top I Full 75% 6 from top About 54% Half full 'i2hw- W. %%L.irS&'W&& m* iB X * 6 & u QI %"tW% 4 P, " b W * l N * l A . :Hydrogen after 1 *minute Hydrogen after 30 Hydrogen after 60 " $ minutes minutes 6.3% As you probably know, H2 has an LEL of 4%. From our measurements, we have determined that the reaction of the silicon with the water is generating H2 in levels above the LEL and creating a flammable headspace. We need help to determine what our options are in terms of eliminating the headspace build-up, proper classification, interactions with the DOT, any exemption opportunities, etc. One of the options we are interested in exploring is the use of a vented cap that allows an 'air exchange' between the headspace and the atmosphere. The thought that if this reaction were allowed to vent, then the LEL would not be reached in the headspace and thus it would be non-hazardous. We are not sure if this is permitted by the DOT or would require an exemption of some sort by the DOT and would like your assistance on that question as well. We were able to obtain a Letter of Interpretation from the DOT that is almost spot on to our situation. The L of I relates to rail cars, but the H2 reaction issue is exactly the type of scenario we have. This has given us some guidance, but takes us down a path that essentially prohibits from using jerricans, drums and totes if I <<>> HydrogenIPackaging Issue am understanding the packaging instructions correctly. I have attached for your review. Possible solutions to consider: 1 . Vented Caps- is a vented cap that allows for pressure release and air exchange permitted that prevents the build-up of hydrogen above the LEL in the headspace of the container. Also, can you look at the attached photos related to 2-way vented caps. It appears these are UN approved and allow for air exchange. These would allow the H2 reaction to vent and disperse to air thus potentially eliminating the H2 generation in the headspace creating a flammable atmosphere. These are used with the totes. Markings on the caps: UN31 HAlNIUSA/+AA2503 Leak Proof Inspection. Is this type of cap in general an option for us? 2. Overpack- can a jerrican of material be placed inside a larger overpack (85 gal) drum that could contain any released hydrogen from the jerrican within the overpack headspace. Also would prevent any potential spillage from jerrican depending on type of cap used. 3. Freezing- could freezing of material which would prevent hydrogen reaction from occurring be used. Material would be shipped as a non-haz solid in jerrican, drum or tote. To confirm, mode of transportation within the U.S. would be ground. Internationally, would need to be able to ship by water. No air shipping expected at this time. From our perspective, the use of an appropriate cap that allows air exchange and venting is the preferred choice. It looks like there may be some options based on some cap information I had sent to you last week. Also, looking at any suggestions you might have that we are missing. Basically, we are looking for ways to get the hydrogen out of the container so that the LEL is not reached while still in compliance with DOT. We are also looking at reformulation options but are somewhat limited right now because we cannot move the material where it needs to go for evaluation and more testing. Namely, from our customer site back to our site. Thanks. <<>> GoreDURAVENT SSSchuetz -40 D38 black SSSchuetz-100 3-4277 1 #481645 3-8172 1 WOO4534 34277 1 a86876 3-8891 / #I270729 4-5039 1 L1199099 4-4121 1#9l3197 3-8861 1 IYJD06747 4-3754 1 #852430 for strong gahing material discharging without (e.g. hydrogene-pemxide) opening of screwcap discharging without opening of screw cap ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `b7e396e5dadaebab5785c375ec7a8111aa6806a29d360f14ceb12cde5396bb06` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-22T11:51:41.228Z - Document slug: `phmsa-interpretation-09-0067` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Cabot Microelectronics" ], "individuals": [ "Mr. Michael Trembley" ], "refIds": [ "09-0067" ], "catalogDates": [ "2009-07-20" ], "catalogParts": [ 173 ], "catalogRowCount": 1, "sourceRecordUrls": [ "https://www.phmsa.dot.gov/node/63056" ], "linkedAttachmentUrls": [], "unavailableResponseUrls": [], "duplicateRepresentationUrls": [], "citedSections": [ "173.24", "173.24(g)(2)" ], "catalogPageUrls": [ "https://www.phmsa.dot.gov/regulations/title49/section/17324" ], "pdfUrls": [ "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretations/2009/090067.pdf" ], "representations": [ { "viewUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretations/2009/090067.pdf", "detailUrl": null, "detailHtmlPath": null, "pdfUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretations/2009/090067.pdf", "pdfArtifactPath": "data/sources/phmsa-interpretations/09-0067-7f8046fbd2.pdf", "pdfArtifactSha256": "b35cc096c4a4cae3a4cf7756d5df556dbe7b25048263eff97510b1b93bcf1c9a", "extractedTextPath": "data/sources/phmsa-interpretations/09-0067-7f8046fbd2.v2.txt", "extractedTextSha256": "6afcb3967a66054a620fdd16027d7cb29238786a98578f924d53f6072c599815", "pageCount": 5, "extractionVersion": 2 } ], "caveat": "Interpretations apply regulations to the facts presented and do not create independently enforceable requirements.", "jurisdiction": "US" } ```