Alessandro MorettiPh.D.Italy
Laser-Based Additive ManufacturingPublished
Dec 24, 2025
Sulfur Dioxide (SO₂)
Chemical Properties
Chemical Identity
CAS Number
7446-09-5
Formula
SO₂
Molecular Weight
64.06 g/mol
Exposure Limits Comparison
OSHA PEL
5 ppm
NIOSH REL
2 ppm
ACGIH TLV
0.25 ppm
Health Effects
Respiratory Irritation
Yes
Bronchospasm
Yes
Asthma Trigger
Yes
Pulmonary Edema
Yes
Sulfur Dioxide (SO₂) safety information
Comprehensive safety and handling requirements
Detection Monitoring
- Electrochemical
- UV fluorescence
- Infrared
- Dräger SO2 0.1/a
- Gastec 5L
- Kitagawa 103
| Sensor Types | ||||||||||
| Detection Range | 0-50 ppm typical | |||||||||
| Alarm Setpoints |
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| Colorimetric Tubes | ||||||||||
| Analytical Methods |
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| Odor Threshold | 0.3-1 ppm - provides adequate warning below toxic levels |
Environmental Impact
| Aquatic Toxicity | Toxic to aquatic life. LC50 (fish, 96h): 100-180 mg/L. Forms acidic solutions. | ||||
| Biodegradability | Reacts in atmosphere. Oxidizes to sulfuric acid. Not biodegradable. | ||||
| Bioaccumulation | Does not bioaccumulate. | ||||
| Soil Mobility | High mobility as gas. Deposits as sulfates. Contributes to soil acidification. | ||||
| Atmospheric Fate | Oxidizes to sulfur trioxide then sulfuric acid. Major acid rain precursor. Atmospheric residence: hours to days. | ||||
| Ozone Depletion | false | ||||
| Reportable Releases |
|
Ppe Requirements
| Respiratory | SCBA or supplied-air respirator for >5 ppm or unknown concentrations. Air-purifying with acid gas cartridge acceptable for ≤5 ppm with escape provisions. |
| Eye Protection | Chemical safety goggles, face shield for liquid contact |
| Skin Protection | Nitrile gloves for liquid contact (cryogenic hazard). Thermal protection for liquefied SO2. |
Reactivity
- Potassium chlorate
- Alkali metals
- Metal oxides
- Halogens
- Ammonia
- Acetylene
- Aluminum
- Sulfur oxides
- Sulfuric acid mist
- Heat
- Moisture (forms sulfurous acid)
- Incompatible materials
| Stability | Stable under normal conditions. |
| Polymerization | Will not polymerize |
| Incompatible Materials | |
| Hazardous Decomposition | |
| Conditions To Avoid | |
| Reactivity Hazard | Reacts with water to form sulfurous acid (corrosive). Reacts violently with metal oxides and alkali metals. |
Regulatory Classification
- Acute toxicity (inhalation)
- Skin corrosion
- Serious eye damage
| Un Number | UN1079 | ||||||
| Dot Hazard Class | 2.3 (Toxic gas) | ||||||
| Dot Label | Poison Gas | ||||||
| Nfpa Codes |
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| Epa Hazard Categories | |||||||
| Sara Title Iii | true | ||||||
| Cercla Rq | 1 pound (0.454 kg) |
Storage Requirements
- Potassium chlorate
- Alkali metals
- Sodium hydride
- Metal oxides
- Aluminum
- Halogens
| Temperature Range | Store cylinders <52°C. Liquefied SO2 requires cryogenic storage. |
| Ventilation | Outdoor storage preferred. Indoor: mechanical ventilation with emergency backup. SO2 gas detection mandatory. |
| Incompatibilities | |
| Container Material | Steel cylinders. Stainless steel for liquid. |
| Segregation | Separate from incompatibles. Corrosive gas storage area. |
| Quantity Limits | Per fire code. Many facilities limit indoor storage. |
| Special Requirements | Cylinder restraints mandatory. Leak detection system required. Post "CORROSIVE GAS" signs. Emergency procedures posted. For liquid: cryogenic handling equipment. |
Produced From Contaminants
Produced From Materials
Exposure Limits
Regulatory exposure thresholds and safe concentration levels
- Osha Pel Ppm
- 5
- Osha Pel Mg M3
- 13
- Niosh Rel Ppm
- 2
- Niosh Rel Mg M3
- 5
- Acgih Tlv Ppm
- 0.25
- Acgih Tlv Mg M3
- 0.65
- Workplace Exposure
- Osha Peltwa_8hr: 5 ppm (13 mg/m³)stel_15min: nullceiling: nullNiosh Reltwa_8hr: 2 ppm (5 mg/m³)stel_15min: 5 ppm (13 mg/m³) - 15 minceiling: nullidlh: 100 ppmAcgih Tlvtwa_8hr: 0.25 ppmstel_15min: nullceiling: nullBiological Exposure Indices
Physical Properties
Physical characteristics and state information
- Boiling Point
- -10.0°C (14°F)
- Melting Point
- -75.5°C (-103.9°F)
- Vapor Pressure
- 2538 mmHg @ 21°C
- Vapor Density
- 2.26 (Air=1)
- Specific Gravity
- 1.43 (liquid @ 0°C)
- Flash Point
- Not applicable (non-flammable)
- Autoignition Temp
- Not applicable
- Explosive Limits
- Not applicable
- Appearance
- Colorless gas, colorless liquid under pressure
- Odor
- Pungent, suffocating odor @ 0.3-1 ppm
Reactivity
Chemical reactivity and compatibility with other substances
- Stability
- Stable under normal conditions.
- Polymerization
- Will not polymerize
- Incompatible Materials
- Potassium chlorate
- Alkali metals
- Metal oxides
- Halogens
- Ammonia
- Acetylene
- Aluminum
- Hazardous Decomposition
- Sulfur oxides
- Sulfuric acid mist
- Conditions To Avoid
- Heat
- Moisture (forms sulfurous acid)
- Incompatible materials
- Reactivity Hazard
- Reacts with water to form sulfurous acid (corrosive). Reacts violently with metal oxides and alkali metals.
Synonyms & Identifiers
Alternative names and chemical identifiers (CAS numbers)
- Synonyms
- Sulfurous anhydride
- Sulfur oxide
- SO2
- Sulphur dioxide
- Common Trade Names
- Other Identifiers
- Rtecs NumberWS4550000Ec Number231-195-2Pubchem Cid1119
