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General information for laboratory, clinic and supply staff. It is not medical advice, not a safety data sheet and not a procedure; follow the product label, the manufacturer’s safety data sheet and your facility’s chemical-safety program.
Short answer
Calcium hypochlorite, Ca(ClO)2, is an inorganic calcium salt supplied as a white granular solid or as tablets pressed from granules. It is a solid-form member of the hypochlorite (chlorine) disinfectant class, alongside liquid sodium hypochlorite. It is also a strong oxidizer, which is why its storage and compatibility rules matter as much as its disinfecting use.
Definition and scope
NIH PubChem (compound record CID 24504, checked 2026-10-30) describes calcium hypochlorite as an inorganic calcium salt whose role is a bleaching agent, and describes the material as a white granular solid, or tablets compressed from the granules, with an odor of chlorine. NOAA CAMEO Chemicals (checked 2026-10-30) lists the formula Ca(ClO)2, UN number 1748 and a DOT oxidizer label. Both sources list water purification, swimming-pool disinfection, and bleaching of paper and textiles among its uses.
This page covers where calcium hypochlorite sits among disinfectants and which materials it should be kept apart from. Pool-shock products are one consumer form of the same chemistry and are not covered here; for the liquid and solid forms side by side, see sodium hypochlorite vs calcium hypochlorite.
How it is classed and used as a disinfectant
The CDC Guideline for Disinfection and Sterilization in Healthcare Facilities (chlorine and chlorine compounds section, checked 2026-10-30) states that hypochlorites are available as liquid (for example sodium hypochlorite) or solid (for example calcium hypochlorite). The CDC lists the following for hypochlorites as a class:
- Advantages: a broad spectrum of antimicrobial activity, no toxic residues, no effect from water hardness, inexpensive and fast acting.
- Disadvantages: corrosiveness to metals at high concentrations (above 500 ppm), inactivation by organic matter, discoloring of fabrics, and release of toxic chlorine gas when mixed with ammonia or acid, for example household cleaning agents.
- The CDC also notes that hypochlorites and other germicides are substantially inactivated in the presence of blood.
The household-bleach percentages and ppm figures in the CDC text refer to sodium hypochlorite, not to calcium hypochlorite. The CDC text gives no strength, dilution or contact time for calcium hypochlorite itself, so this page gives none either. For the liquid form see bleach concentration and bleach shelf life; for the wider classes, see types of disinfectants.
Incompatibility checklist for storage areas
Because calcium hypochlorite is an oxidizer, the question for staff is usually what it must not touch. Each row below traces to the named source.
| Do not bring into contact with | What the source says | Source |
|---|---|---|
| Acids | Evolves highly toxic chlorine gas on contact with acids; the CDC also warns of toxic chlorine gas when hypochlorite is mixed with acid cleaners. | NOAA CAMEO Chemicals; CDC |
| Ammonia or urea | Forms highly explosive NCl3 on contact; the CDC warns of toxic gas release with ammonia. | NOAA CAMEO Chemicals; CDC |
| Organic matter, oil, hydrocarbons, alcohols | Reactions may lead to explosions; reactions with methanol, ethanol and other alcohols can become violent after a delay. | NOAA CAMEO Chemicals |
| Heat or fire | Decomposes when heated, releasing oxygen and chlorine gases; prolonged exposure to fire or heat may cause vigorous decomposition and container rupture. | NOAA CAMEO Chemicals; NIH PubChem |
| Combustible materials | Noncombustible itself, but will accelerate the burning of combustible materials. | NIH PubChem |
| Water | Water soluble and slowly decomposed by water, with evolution of chlorine and heat, although CAMEO also cites experimental work finding essentially no Cl2 gas formation under normal conditions. | NOAA CAMEO Chemicals |
This table is the reason calcium hypochlorite belongs on a segregation plan with other oxidizers; see chemical storage compatibility and segregation rules for how facilities group incompatible classes.
Where it matters for labs, clinics and supply decisions
- Labels and hazard class. The UN 1748 number and DOT oxidizer label (CAMEO) mean the product is handled as a regulated oxidizer in shipping and storage, not as an ordinary cleaning product.
- Organic load. The CDC notes that hypochlorites are inactivated by organic matter and substantially inactivated in the presence of blood.
- Metal surfaces. The CDC lists corrosiveness to metals at high concentrations as a class limit, which matters for stainless equipment and instruments.
- Granules in use. The CDC notes that chlorine-releasing granules can generate chlorine fumes when applied to urine, an example of the ammonia and urea pairing in the table.
For how disinfectant labels are read generally, see what is disinfectant spray.
Common misunderstandings
Is calcium hypochlorite the same as household bleach?
No. Household bleach is a liquid sodium hypochlorite solution (5.25-6.15% in the CDC text). Calcium hypochlorite is the solid form of the same hypochlorite class. Strengths quoted for bleach should not be carried over to the solid.
Does mixing it with another cleaner make it stronger?
No. Per the CDC and CAMEO, mixing with acids or ammonia releases toxic gas, and with urea can form an explosive compound. Hypochlorite should not be combined with other chemicals.
FAQ
What is calcium hypochlorite?
An inorganic calcium salt, Ca(ClO)2, supplied as a white granular solid or as tablets pressed from granules, with an odor of chlorine (NIH PubChem).
What is calcium hypochlorite used for?
PubChem lists water purification, swimming-pool disinfection, and bleaching of paper and textiles. The CDC names it as the example of a solid hypochlorite disinfectant.
Which materials must it not contact?
See the incompatibility checklist above: acids, ammonia or urea, organic matter, oils, hydrocarbons and alcohols, heat or fire, and combustible materials.
Sources
- CDC, Guideline for Disinfection and Sterilization in Healthcare Facilities: Chemical Disinfectants (chlorine and chlorine compounds). Checked 2026-10-30.
- NIH National Library of Medicine, PubChem: Calcium hypochlorite, CID 24504. Checked 2026-10-30.
- NOAA, CAMEO Chemicals: Calcium hypochlorite. Checked 2026-10-30.
