Calcium Oxide

1Identification

Name

Calcium Oxide

IUPAC name

oxocalcium

CAS number

1305-78-8

EC number

215-138-9

Molecular formula

CaO

Molecular weight

56.08 g/mol

InChIKey

ODINCKMPIJJUCX-UHFFFAOYSA-N

SMILES

O=[Ca]

PubChem CID

14778

Synonyms

Calcia, Calxyl, Gebrannter kalk, Unslaked lime, Calcium monoxide, Airlock, CALX, Calx usta, Chaux vive, Quick lime, Rhenosorb C, Rhenosorb F, Calcium oxide (CaO), Desical P

Recommended uses

• Used in building materials (bricks, plaster, mortar, and stucco); to make aluminum, magnesium, calcium salts, and glass; to dehair hides; to process non-ferrous ores; to produce paper pulp; and to clarify cane and beet sugar juices; Also used in drilling fluids, lubricants, and water treatment; [HSDB]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• Aluminum Producing [Category: Industry] Pulp and Paper Processing [Category: Industry] Sewer and Wastewater Treatment [Category: Industry] Leather Tanning and Processing [Category: Industry] Cement Producing [Category: Industry] Glass Manufacturing [Category: Industry] Metal Extraction and Refining [Category: Industry]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
• For calcium oxide (USEPA/OPP Pesticide Code: 075604) ACTIVE products with label matches. /SRP: Registered for use in the USA but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./
  Hazardous Substances Data Bank (HSDB)
• Other Binder Processing aids not otherwise specified Antioxidant pH regulating agent Dust suppressant Abrasives Chemical reaction regulator Dehydrating agent (desiccant) Absorbent Flux agent Soil amendments (fertilizers) Catalyst Thickening agent Waterproofing agent Corrosion inhibitor Filler Not Known or Reasonably Ascertainable Stabilizing agent Sealant (barrier) Intermediate Processing aids, specific to petroleum production Adhesion/cohesion promoter Drier Solids separation (precipitating) agent, not otherwise specified Chelating agent Oxidizing agent Adsorbent Humectant
  EPA Chemical Data Reporting (CDR)
• Other Binder Abrasives Processing aids not otherwise specified Not Known or Reasonably Ascertainable Filler Catalyst Soil amendments (fertilizers) Dehydrating agent (desiccant) Adsorbent Intermediate
  EPA Chemical Data Reporting (CDR)

Use categories: Food additives · Food Additives -> ACIDITY_REGULATOR; FLOUR_TREATMENT_AGENT; YEAST_FOOD -> JECFA Functional Classes · Cosmetics -> Buffering

Description

• Calcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.
  CAMEO Chemicals
• Calcium oxide is a member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio. It has a role as a fertilizer.
  ChEBI
• Lime is a mineral with formula of CaO. The IMA symbol is Lm.
  RRUFF Project

2Hazard identification

Signal word

Danger

Pictograms

GHS05, GHS07

Classification source

European Chemicals Agency (ECHA)

Precautionary statements

Other reported classifications

4 classification records exist across sources. Differences usually reflect purity, physical form or impurities.

Health hazards

• Causes burns on mucous membrane and skin. Inhalation of dust causes sneezing. (USCG, 1999)
  CAMEO Chemicals
• · TOXIC and/or CORROSIVE; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. · Reaction with water or moist air may release toxic, corrosive or flammable gases. · Reaction with water may generate much heat that will increase the concentration of fumes in the air. · Fire will produce irritating, corrosive and/or toxic gases. · Runoff from fire control or dilution water may be corrosive and/or toxic and cause environmental contamination.
  Emergency Response Guidebook (ERG)

Fire hazards

• Excerpt from ERG Guide 157 [Substances - Toxic and/or Corrosive (Non-Combustible / Water-Sensitive)]: Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above 65%) may act as oxidizers. Also consult ERG Guide 140. Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.). Substance may react with water (some violently), releasing corrosive and/or toxic gases and runoff. Corrosives in contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water. (ERG, 2024)
  CAMEO Chemicals
• · Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. · UN1802, UN2032, UN3084, UN3093, UN1796 (above 50%), UN1826 (above 50%), and UN2031 (above 65%) may act as oxidizers. Also consult GUIDE 140. · Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars, etc.). · Substance may react with water (some violently), releasing corrosive and/or toxic gases and runoff. · Corrosives in contact with metals may evolve flammable hydrogen gas. · Containers may explode when heated or if contaminated with water.
  Emergency Response Guidebook (ERG)
• Not combustible.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Hazards summary

• Can cause first degree burns on short exposure and second degree burns on long exposure; [CHRIS] May be corrosive to the skin, eyes, and respiratory tract; May cause ulceration and perforation of the nasal septum; [ICSC]
  Haz-Map, Information on Hazardous Chemicals and Occupational Diseases

3Composition / information on ingredients

This page describes the pure substance. Commercial products may be solutions or mixtures. Check Section 3 of your supplier's SDS for concentrations and other ingredients.

4First-aid measures

• Excerpt from NIOSH Pocket Guide for Calcium oxide: Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: WATER FLUSH IMMEDIATELY - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly. Breathing: RESPIRATORY SUPPORT - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once.
  CAMEO Chemicals
• General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped with a one-way valve or other device).
  Emergency Response Guidebook (ERG)
• (General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly. Breathing: Respiratory support Swallow: Medical attention immediately - If this chemical has been swallowed, get medical attention immediately.
  The National Institute for Occupational Safety and Health (NIOSH)

Symptoms of exposure

• Burning sensation. Cough. Shortness of breath. Sore throat.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Dry skin. Redness. Skin burns. Burning sensation. Pain.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Redness. Pain. Blurred vision. Severe deep burns.
  ILO-WHO International Chemical Safety Cards (ICSCs)

5Fire-fighting measures

• Extinguish fire using agent suitable for surrounding fire. Use flooding quantities of water as spray. DO NOT use carbon dioxide or halogenated extinguishing agents.
  Hazardous Substances Data Bank (HSDB)
• If material involved in fire: Extinguish fire using agent suitable for type of surrounding fire. (Material itself does not burn or burns with difficulty.) Cool all affected containers with flooding quantities of water. Do not use water on material itself. Keep run-off out of sewers and water sources. Use foam, dry chemical, or carbon dioxide.
  Hazardous Substances Data Bank (HSDB)
• In case of fire in the surroundings, use appropriate extinguishing media.
  Hazardous Substances Data Bank (HSDB)

6Accidental release measures

Isolation and evacuation

• Excerpt from ERG Guide 157 [Substances - Toxic and/or Corrosive (Non-Combustible / Water-Sensitive)]: IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids. SPILL: Increase the immediate precautionary measure distance, in the downwind direction, as necessary. FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)
  CAMEO Chemicals
• Immediate precautionary measure · Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids. Spill · For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances. · For non-highlighted materials: increase the immediate precautionary measure distance, in the downwind direction, as necessary. Fire · If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions.
  Emergency Response Guidebook (ERG)

Spill cleanup

• Personal protection: particulate filter respirator adapted to the airborne concentration of the substance. Sweep spilled substance into covered dry containers.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• 1) Ventilate area of spill. 2) Collect spilled material in most convenient and safe manner and deposit in sealed containers for reclamation or for disposal in secured sanitary landfill.
  Hazardous Substances Data Bank (HSDB)
• Environmental considerations: Land spill: Dig a pit, pond, lagoon, holding area to contain liquid or solid material. /SRP: If time permits, pits, ponds, lagoons, soak holes, or holding areas should be sealed with an impermeable flexible membrane liner./ Cover solids with a plastic sheet to prevent dissolving in rain or fire fighting water. Dike surface flow using soil, sand bags, foamed polyurethane, or foamed concrete.
  Hazardous Substances Data Bank (HSDB)
• Environmental considerations: Water spill: Use natural barriers or oil spill control booms to limit spill travel. Use natural deep water pockets, excavated lagoons, or sand bag barriers to trap material at bottom. Remove trapped material with suction hoses.
  Hazardous Substances Data Bank (HSDB)

7Handling and storage

• Separated from strong acids, organic chemicals, water and food and feedstuffs. Dry.
  ILO-WHO International Chemical Safety Cards (ICSCs)
• Keep tightly closed and dry.
  Hazardous Substances Data Bank (HSDB)
• Materials which are toxic as stored or which can decompose into toxic components ... should be stored in a cool well ventilated place, out of the direct rays of the sun, away from areas of high fire hazard, and should be periodically inspected. Incompatible materials should be isolated ...
  Hazardous Substances Data Bank (HSDB)
• Store in a cool, dry, well-ventilated location.
  Hazardous Substances Data Bank (HSDB)

8Exposure controls / personal protection

Personal protective equipment

• Excerpt from NIOSH Pocket Guide for Calcium oxide: Skin: PREVENT SKIN CONTACT - Wear appropriate personal protective clothing to prevent skin contact. Eyes: PREVENT EYE CONTACT - Wear appropriate eye protection to prevent eye contact. Wash skin: • WHEN CONTAMINATED - The worker should immediately wash the skin when it becomes contaminated. • DAILY - The worker should wash daily at the end of each work shift, and prior to eating, drinking, smoking, etc. Remove: WHEN WET OR CONTAMINATED - Work clothing that becomes wet or significantly contaminated should be removed and replaced.
  CAMEO Chemicals
• Protective gloves, goggles, and any type of respirator prescribed for fine dust.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate personal protective clothing to prevent skin contact.
  Hazardous Substances Data Bank (HSDB)
• Wear appropriate eye protection to prevent eye contact.
  Hazardous Substances Data Bank (HSDB)

Respirator recommendations

• NIOSH Up to 10 mg/m3 : (APF = 5) Any quarter-mask respirator. Click here for information on selection of N, R, or P filters. Up to 20 mg/m3 : (APF = 10) Any particulate respirator equipped with an N95, R95, or P95 filter (including N95, R95, and P95 filtering facepieces) except quarter-mask respirators. The following filters may also be used: N99, R99, P99, N100, R100, P100. Click here for information on selection of N, R, or P filters.
  The National Institute for Occupational Safety and Health (NIOSH)

9Physical and chemical properties

10Stability and reactivity

Reactivity

• A base and an oxidizing agent. Neutralizes acids with generation of heat. Nonflammable, but will support combustion by liberation of oxygen, especially in the presence of organic materials. Reacts very violently with liquid hydrofluoric acid [Mellor 2, Supp. 1:129 1956]. Reacts extremely violently with phosphorus pentaoxide when reaction is initiated by local heating [Mellor 8 Supp.3:406 1971].
  CAMEO Chemicals
• Crumbles on exposure to moist air. Reacts with water to form corrosive calcium hydroxide, with evolution of much heat. Temperatures as high as 800 °C have been reached with addition of water (moisture in air or soil). The heat of this reaction has caused ignition of neighboring quantities of sulfur, gunpowder, wood, and straw [Mellor 3: 673 1946-47].
  CAMEO Chemicals

Incompatible materials and hazardous reactions

• Addn of water to quicklime has generated temp as high as 800 °C. Some reports describe reaction as violent. Ignition of sulfur, gunpowder, wood, and straw by heat of quicklime-water reaction has been reported.
  Hazardous Substances Data Bank (HSDB)
• Even when cold, fluorine will attack calcium oxide, evolving much heat and some light.
  Hazardous Substances Data Bank (HSDB)
• Chlorine trifluoride reacts violently, producing flame, with...calcium oxide.
  Hazardous Substances Data Bank (HSDB)

Chemical stability

• Readily absorbs carbon dioxide and water from air, becoming airslaked.
  Hazardous Substances Data Bank (HSDB)

11Toxicological information

Target organs

• Eyes, skin, respiratory system
  The National Institute for Occupational Safety and Health (NIOSH)

Short-term exposure effects

• The substance is corrosive to the eyes, skin and respiratory tract. The effects may be delayed. Medical observation is indicated.
  ILO-WHO International Chemical Safety Cards (ICSCs)

Long-term exposure effects

• Repeated or prolonged contact with skin may cause dermatitis. Repeated or prolonged inhalation of dust particles may cause effects on the lungs. Repeated or prolonged inhalation may cause nasal ulceration. This may result in perforation of the nasal septum.
  ILO-WHO International Chemical Safety Cards (ICSCs)

12Ecological information

Not available in the public sources we compile. Check Section 12 of the supplier's SDS.

13Disposal considerations

• SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal and plant life; and conformance with environmental and public health regulations.
  Hazardous Substances Data Bank (HSDB)
• SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal.
  Hazardous Substances Data Bank (HSDB)
• ... May be disposed of in sealed containers in secured sanitary landfill.
  Hazardous Substances Data Bank (HSDB)

14Transport information

UN numbers: UN 1910, UN 1826, UN 2031, UN 2032

Shipping name

• UN 1910; Calcium oxide
  Hazardous Substances Data Bank (HSDB)

DOT hazard class

• Calcium oxide
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• UN1910
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172
• Class 8 Corrosive material (49 eCFR § 173.136)
  US Code of Federal Regulations, Hazardous Materials, 49 CFR Part 172

DOT label

• Corrosive
  CAMEO Chemicals

UN classification

• UN Hazard Class: 8; UN Pack Group: III
  ILO-WHO International Chemical Safety Cards (ICSCs)

Emergency Response Guidebook

• 1910 157
  Emergency Response Guidebook (ERG)

How DOT hazard classes work →

15Regulatory information

• Residues of calcium oxide are exempted from the requirement of a tolerance when used in accordance with good agricultural practice as inert (or occasionally active) ingredients in pesticide formulations applied to growing crops or to raw agricultural commodities after harvest. Use: solid diluent, carrier.
  Hazardous Substances Data Bank (HSDB)
• Substance added directly to human food affirmed as generally recognized as safe (GRAS).
  Hazardous Substances Data Bank (HSDB)

Overview of SDS regulations (OSHA HazCom, WHMIS, REACH/CLP) →

16Other information

Compiled from PubChem CID 14778 and the sources it aggregates (attributed inline). Data retrieved 2026-10-12. This summary describes the pure substance and is not a supplier SDS.