Hazardous Materials

Hazardous Materials#

Reference of hazardous-materials classification systems an operator may meet in transport, response, or facility investigation: UN-class numbers, NFPA 704 fire-diamond, GHS pictograms, and HAZWOPER response levels.

For broader incident-response context, see Security and Digital Forensics.

UN dangerous-goods classes#

Class	Notes
1 Explosives	1.1 mass-explosion / 1.2 projection / 1.3 fire / 1.4 minor hazard / 1.5 very insensitive / 1.6 extremely insensitive.
2 Gases	2.1 flammable / 2.2 non-flammable / 2.3 toxic.
3 Flammable liq.	closed-cup flashpoint <= 60.5 °C.
4 Flammable solid	s 4.1 flammable / 4.2 spontaneously combustible / 4.3 dangerous when wet.
5 Oxidising	5.1 oxidiser / 5.2 organic peroxide.
6 Toxic / Inf.	6.1 toxic / 6.2 infectious.
7 Radioactive	yellow-II / yellow-III / white-I labels by activity + shielding.
8 Corrosive	acids + bases.
9 Misc. dangerous	lithium batteries (UN 3480/3481/3090/3091), environmentally hazardous, asbestos, dry ice, etc.

UN four-digit numbers (e.g. UN 1170 = ethanol) sit on the placard above the class number; the catalog is the UN Recommendations on the Transport of Dangerous Goods (Orange Book).

NFPA 704 fire diamond#

The NFPA 704 standard places four color-coded diamonds inside the larger placard:

Position / color	Meaning
Blue (left)	Health hazard (0-4).
Red (top)	Flammability (0-4).
Yellow (right)	Instability / reactivity (0-4).
White (bottom)	Special notice: `OX` (oxidiser), `W` (water- reactive, with line through), `SA` (simple asphyxiant), `COR` / `ACID` / `ALK` (corrosive), `BIO` / `RAD` (legacy biohazard / radioactive).

Numeric scale 0-4 (any position):

Level	Health / fire / reactivity meaning
0	minimal hazard.
1	slight; could cause significant irritation.
2	moderate; temporary or minor injury.
3	serious; major injury possible.
4	severe; death or major permanent injury possible (health); gas / very volatile liquid that ignites at ambient temp (fire); detonates at normal temperature / pressure (reactivity).

GHS pictograms#

Globally Harmonized System; the diamond-on-point red-bordered pictograms on chemical packaging:

Pictogram	Hazard
Flame	flammables.
Flame over circle	oxidisers.
Exploding bomb	explosives + self-reactives.
Skull and cross.	acute toxicity.
Health hazard	carcinogen / mutagen / respiratory sensitiser / reproductive toxin / target-organ.
Exclamation mark	irritant / harmful / sensitiser (skin).
Corrosion	corrosive to skin / eyes / metals.
Gas cylinder	gases under pressure.
Environment	aquatic toxicity (non-mandatory in US).

HAZWOPER PPE levels#

US OSHA 29 CFR 1910.120 personal protective levels (descending order of protection):

Level	PPE
Level A	fully encapsulating chemical-protective suit + SCBA (positive-pressure self-contained breathing apparatus); highest skin + respiratory protection.
Level B	SCBA + chemical-resistant suit (non-encapsulating); high respiratory + lower skin.
Level C	air-purifying respirator (APR / PAPR) + chemical- resistant clothing.
Level D	work uniform; no respiratory protection; for known non-hazardous environments.

Biosafety levels (BSL)#

Level	Notes
BSL-1	minimal-risk; teaching labs (e.g. E. coli K-12).
BSL-2	moderate; agents that cause human disease but treatable (HIV, Salmonella, Staphylococcus).
BSL-3	aerosol-transmissible; serious / lethal but treatable (TB, SARS-CoV-1/2, Bacillus anthracis).
BSL-4	aerosol-transmissible; serious / lethal + no treatment (Ebola, Marburg, Lassa, smallpox). Positive-pressure suits + airlocks.

USDA / APHIS adds BSL-3 Ag and BSL-4 Ag for high- consequence livestock pathogens.

Animal biosafety: ABSL-1 / ABSL-2 / ABSL-3 / ABSL-4 mirror the above for animal facilities.

Radiation levels#

Concept	Notes
Sv (sievert)	SI dose-equivalent; 1 Sv = 100 rem (legacy).
Gy (gray)	SI absorbed dose; 1 Gy = 100 rad.
Bq (becquerel)	SI activity; 1 disintegration / second.
Ci (curie)	legacy activity; 1 Ci = 3.7 × 10^10 Bq.
Background	~3-5 mSv/year from cosmic + terrestrial + radon.
Threshold (sym.)	100 mSv acute = symptomatic acute radiation syndrome risk.
LD50 / 30	~3.5-5 Gy whole-body single dose without medical care.
Lifetime cancer	each Sv adds ~5% lifetime cancer risk (linear no- threshold model).
INES	International Nuclear Event Scale (0-7); 7 = TMI was 5, Chernobyl + Fukushima Daiichi were 7.

Chemical reference#

System	Notes
CAS Registry No.	unique identifier per substance (e.g. 7732-18-5 = water).
SMILES	chemical structure as a string.
InChI / InChIKey	IUPAC International Chemical Identifier.
EC Number	European inventory.
DOT / UN Number	transport identifier (above).
RTECS	Registry of Toxic Effects of Chemical Substances.
HMIS	Hazardous Materials Identification System (NPCA); color-coded similar to NFPA but person-protection rated.
WHMIS	Workplace Hazardous Materials Information System (Canada); now aligned with GHS.

HAZMAT placards (transport)#

Placard type	Notes
Class diamond	UN-class number (above) on colored background; four-digit UN-number sometimes embedded.
Subsidiary diamond	for materials with multiple hazards.
Marine pollutant	fish + tree symbol.
Elevated temp.	“HOT” placard for materials transported at >100 °C.
Fumigation warning	on closed cargo containers.
Limited Quantity	black-and-white diamond-on-square; reduced packaging requirements.
Empty placard	residue still classified.

Operator notes#

NFPA 704 vs HMIS, both use 0-4 color scales but the white quadrant differs (NFPA = special hazards; HMIS = PPE letter A-X). Don’t conflate.
Pictograms vs placards, GHS pictograms label individual chemical containers; UN-class placards label transport vehicles + intermodal containers.
48-hour latency, many chemical exposures present symptoms hours / days later; document immediately.
SDS (Safety Data Sheet, GHS-aligned) is the 16-section reference per chemical; superseded MSDS in 2015.
Lithium batteries are class 9 + sub-categories; air transport heavily regulated post-incident series.
Authorization, HAZMAT response in the US requires HAZWOPER training (40-hour or 24-hour); overseas similar. Operators should not enter contaminated areas without it.