Three types of TLVs for chemical substances are defined:
Threshold limit value - Time weighted average (TLV-TWA): average exposure on the basis of a 8h/day, 40h/week work schedule
Threshold limit value - Short-term exposure limit (TLV-STEL): spot exposure for a duration of 15 minutes, that cannot be repeated more than 4 times per day with at least 60 minutes between exposure periods
Threshold limit value - Ceiling limit (TLV-C): absolute exposure limit that should not be exceeded at any time
Threshold Limit Values for Chemical substances and Biological Exposure Indices
© 2005 ACGIH® and 2012 additions for critical effects!!!
Aerozine 50 - UDMH/Hydrazine & Air, leaks from the missile in normal operations.
Skin notations means that UDMH and the other byproduct chemicals entered the skin as much as inhaling it.
Substance [CAS No.] TWA STEL Notations MW TLV® Basis — Critical Effect(s)
Hydrazine [302-01-2] 0.01 ppm Skin; A3 32.05 Irritation; liver, URT cancer
1,1-Dimethylhydrazine [57-14-7] 0.01 ppm — Skin; A3 60.12 Irritation; neoplasia, URT irr; nasal cancer
N-Nitrosodimethylamine [62-75-9] —(L) — Skin; A3 74.08 Liver, Liver & kidney cancer; liver damage
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Aerozine 50 - UDMH/Hydrazine leaks, air and copper contact: Production of NDMA occurred even at copper concentrations of < 1 ppm. N-Nitrosodimethylamine. Reference: http://www.ncbi.nlm.nih.gov/pubmed/7953474
Substance [CAS No.] TWA STEL Notations MW TLV® Basis — Critical Effect(s)
N-Nitrosodimethylamine [62-75-9] —(L) — Skin; A3 74.08 Liver, Liver & kidney cancer; liver damage
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Aerozine 50 - UDMH/Hydrazine leaks, air and copper add Hydrogen Peroxide as a dilution: Dimethylamine, methanol, formaldehyde dimethylhydrazone, formaldehyde hydrazone, tetramethyltetrazene .Reference: http://www.ncbi.nlm.nih.gov/pubmed/7953474 also USAF 392d Medical Group at Vandenberg AFB 1962 mentioned dilution of Aerozine with Hydrogen Peroxide in spill situations.
Substance [CAS No.] TWA STEL Notations MW TLV® Basis — Critical Effect(s)
Methanol [67-56-1] 200 ppm 250 ppm Skin; BEI 32.04 CNS; Neuropathy; vision; Headache; eye damage;dizziness;
Formaldehyde hydrazone http://www.ncbi.nlm.nih.gov/pubmed/3335049 mutagenic (nih.gov)
Dimethylamine [124-40-3] 5 ppm 15 ppm A4 45.08 Irritation, URT irr; GI damage
Formaldehyde Dimethylhydrazone http://www.chemspider.com/Chemical-Structure.67422.html mutagenic (nih.gov) http://www.ncbi.nlm.nih.gov/pubmed/7953474
Tetramethyltetrazene CAS NO.6130-87-6 http://www.lookchem.com/Tetramethyl-2-tetrazene/ mutagenic (nih.gov) degenerative changes
Tetramethyl-2-tetrazene (CAS NO.6130-87-6) is also called 1,1,4,4-Tetramethyl-2-tetrazene ; 1,1,4,4-Tetramethyltetrazene ; 4-04-00-03427 (Beilstein Handbook Reference) ; BRN 1752817 ; NSC 38247 ; Tetramethyltetrazene ; Tetramethyltetrazone
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Aerozine-50 leaks-UDMH part & just atmospheric oxygen: formaldehyde dimethyl hydrazone (FDH) is a major oxidation product In the UDMH/air reaction REFERENCE: 1984 AIR FORCE ENGINEERING AND SERVICES CENTER TYNDALL AIR FORCE BASE, Florida
Substance [CAS No.] TWA STEL Notations MW TLV® Basis — Critical Effect(s)
Formaldehyde Dimethyl hydrazone http://www.chemspider.com/Chemical-Structure.67422.html mutagenic (nih.gov) http://www.ncbi.nlm.nih.gov/pubmed/7953474
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BYPRODUCT CHEMICALS after spills & DILUTION WITH WATER in the silo during PTS operations and 6 weeks after. Formaldehyde (HCHO), Hydrogen Cyanide (HCN), Ammonia (NH3), (Dinitrogen Tetroxide Nitrogen dioxide) (N2O4), Methylamine (CH3NH2 ), Cyanic Acid (CHNO), Carbon Dioxide (CO2), Carbon Monoxide (CO)’ N-nitrosodimethylamine (CH3)2 NH. REFERENCE: USAF 392d Medical Group at Vandenberg AFB 1962.
Substance [CAS No.] TWA STEL Notations MW TLV® Basis — Critical Effect(s)
Formaldehyde [50-00-0] — C 0.3 ppm SEN; A2 30.03 Irritation; cancer (nasal), URT & eye irr
Methylamine [74-89-5] 5 ppm 15 ppm — 31.06 Irritation, Eye, skin, & URT irritation
Hydrogen cyanide [74-90-8] C 4.7 ppm Skin 27.03 CNS; irritation; anoxia; lung; thyroid, URT irr; headache; nausea; thyroid eff
Ammonia [7664-41-7] 25 ppm 35 ppm — 17.03 Irritation, Eye damage; URT irritation
Nitrogen dioxide [10102-44-0] 0.2 ppm 1 ppm A4 46.01 Irritation; pulmonary edema(2012)
N-Nitrosodimethylamine [62-75-9] —(L) — Skin; A3 74.08 Liver, Liver & kidney cancer; liver damage