{"hq_id":"hq-p-hom-000289","name":"Swimming Pool Shock Treatment — Calcium Hypochlorite (Super-Chlorination, Chlorine Gas Release, Fire Hazard, Chemical Incompatibility)","category":{"primary":"home_cleaning","secondary":"pool_chemical","tags":["calcium hypochlorite","pool shock","super-chlorination","chlorine","oxidizer","fire hazard","chemical incompatibility","pool chemical","Cal-Hypo"]},"product_tier":"HOM","overall_risk_level":"high","description":"Calcium hypochlorite (Ca(OCl)2, 'Cal-Hypo') pool shock treatment is a powerful oxidizing agent sold in granular form at 65-78% available chlorine concentration — used for weekly 'shocking' of swimming pools to destroy chloramines, algae, and organic contaminants by raising free chlorine to 10-30 ppm (versus normal maintenance levels of 1-3 ppm). Cal-Hypo is one of the most hazardous consumer chemicals sold without restriction: it is a strong oxidizer (NFPA 3/0/1 OX) that can spontaneously ignite on contact with organic materials (oil, grease, wood, fabric, body fluids), reacts violently with acids (generating concentrated chlorine gas), absorbs atmospheric moisture to form hypochlorous acid with progressive decomposition, and has been responsible for numerous residential garage fires, chemical burn injuries, and fatal chlorine gas inhalation events. CPSC documented over 4,800 pool chemical-related injuries requiring emergency department treatment annually, with Cal-Hypo involved in the majority of serious events. The compound is classified as an oxidizer for shipping (UN 2880, Class 5.1) and must be stored separately from all other pool chemicals — cross-contamination between Cal-Hypo and trichloroisocyanuric acid (trichlor, another common pool sanitizer) has caused violent exothermic reactions and warehouse fires.","synthesis":{"derived_risk_level":"moderate_to_high","synthesis_confidence":0.673,"synthesis_method":"compound_composition","context_used":"human_child","context_source":"product_users","exposure_modifier":1,"vulnerability_escalated":true,"escalation_reason":"Child exposure group","compounds_resolved":1,"compounds_total":1,"synthesis_date":"2026-05-09","synthesis_version":"1.2.0","methodology_note":"exposure_modifier and adjusted_magnitude are computed from ALETHEIA-calibrated heuristics (route × duration × frequency multipliers, clamped to [0.5, 1.4]). Multipliers are directionally informed by EPA Exposure Factors Handbook (2011) and CalEPA OEHHA but are not regulatory consensus. See /api/methodology for full disclosure."},"hazard_summary":{"sensitive_populations":"children with pool access (chemical stored in accessible locations), homeowners without chemical handling training, individuals with asthma (chlorine gas bronchospasm), storage neighbors of incompatible pool chemicals","overall_risk":"high","primary_concerns":["Strong oxidizer: spontaneous combustion on contact with organic materials — garage and storage shed fire hazard","Chlorine gas generation when mixed with acids or other pool chemicals — potentially lethal in enclosed spaces","4,800+ pool chemical ER injuries annually — Cal-Hypo involved in majority of serious events","Cross-contamination with trichlor (another pool chemical) causes violent exothermic reaction and fire"],"exposure_routes":"Inhalation (chlorine gas from acid contact or wet decomposition; Cal-Hypo dust during handling). Dermal (granules cause chemical burns on moist skin). Ocular (dust and splash — severe corneal injury). Ingestion (accidental — children accessing stored granules)."},"exposure":{"routes":["inhalation","dermal","ocular","ingestion"],"contact_types":["inhalation_acute","dermal_direct","ocular_splash","ingestion_accidental"],"users":["adult","child","pool_maintenance_worker"],"duration":"acute","frequency":"weekly_seasonal","scenarios":["Homeowner adds Cal-Hypo shock directly to pool skimmer basket — concentrated chlorine gas release in pump room causes respiratory distress","Cal-Hypo granules contact damp organic material in storage shed — spontaneous combustion and fire","Pool owner mixes Cal-Hypo with muriatic acid (HCl) for 'faster results' — violent reaction releasing concentrated chlorine gas","Wind blows Cal-Hypo dust into eyes during pool-side application — immediate severe chemical conjunctivitis and corneal burn"],"notes":"Calcium hypochlorite: CAS 7778-54-3; MW 142.98; 65-78% available chlorine. Strong oxidizer: NFPA Hazard Diamond 3/0/1/OX. Fire hazard: Ca(OCl)2 + organic material (oil, grease, wood, charcoal, fabric) → exothermic decomposition → spontaneous combustion. Acid reaction: Ca(OCl)2 + 2HCl → CaCl2 + Cl2 (gas) + H2O. Cross-contamination: Cal-Hypo + trichlor (trichloroisocyanuric acid) → violent exothermic reaction, fire, Cl2 release. CPSC: 4,800 pool chemical ER injuries/year; Cal-Hypo and muriatic acid account for majority. Proper application: dissolve Cal-Hypo in bucket of water BEFORE adding to pool; never add through skimmer. UN 2880 (Calcium hypochlorite, hydrated), Class 5.1 oxidizer for transport."},"consumer_guidance":{"usage_warning":"ALWAYS pre-dissolve Cal-Hypo granules in a bucket of water before adding to the pool — never add dry granules directly to pool or through skimmer (concentrated gas in pump room). NEVER mix Cal-Hypo with ANY other pool chemical, especially muriatic acid (HCl) or trichlor (chlorine tablets). Store in original container in a cool, dry, well-ventilated area separate from ALL other chemicals, fuels, and organic materials. Keep dry at all times — moisture initiates decomposition. Wear safety goggles, chemical-resistant gloves, and dust mask when handling granules. Keep children completely away from pool chemical storage.","safer_alternatives":["Liquid sodium hypochlorite (12.5%) — non-oxidizer for storage, no dust, easier to handle","Salt chlorine generators (electrolytic) — produce chlorine on-demand from dissolved salt, no chemical handling","UV/ozone supplemental sanitation reducing chemical shock frequency","Pool maintenance service eliminating homeowner chemical handling entirely"]},"regulatory":{"applicable_regulations":[{"jurisdiction":"USA","regulation":"DOT Hazardous Materials Transport for Calcium Hypochlorite and CPSC Pool Chemical Safety","citation":"49 CFR 172 (DOT) UN 2880, Class 5.1 Oxidizer; CPSC 16 CFR 1500 (FHSA)","requirements":"Calcium hypochlorite classified as Class 5.1 oxidizer for transport (UN 2880). FHSA requires labeling as 'DANGER: Strong Oxidizer' with precautionary statements against mixing with other chemicals. No child-resistant packaging requirement for pool chemicals — CPSC has investigated but not mandated. NFPA 400 (Hazardous Materials Code) governs storage requirements including separation distances from incompatible materials. Some states require pool chemical safety fencing.","compliance_status":null,"effective_date":null,"enforcing_agency":"DOT / CPSC / State fire marshals / NFPA","penalties":null,"source_ref":null}],"certifications":[],"labeling":{"required_disclosures":[],"prop65_warning":{"required":null,"chemicals":[],"endpoint":null,"notes":null},"ghs_labeling":{"required":null,"signal_word":null,"pictograms":[],"hazard_statements":[],"notes":null},"hidden_ingredients":{"trade_secret_protected":null,"categories_hidden":[],"estimated_count":null,"known_concerns":null,"notes":null},"notes":null},"recalls":[],"regulatory_gap":null,"notes":null},"lifecycle":{"recyclable":false,"disposal_guidance":"Expired or degraded Cal-Hypo must be dissolved in large volumes of water and carefully added to pool water or disposed through hazardous waste collection. Never dispose of dry Cal-Hypo in trash — contact with organic waste materials can cause fire.","hazardous_waste":true,"expected_lifespan":"1-2 year shelf life if kept dry and sealed; degrades to CaCO3 and CaCl2 on moisture exposure; discard if product has strong chlorine odor in sealed container (indicates active decomposition)"},"formulation":{"form":"varies","key_ingredients":[],"certifications":[]},"materials":{"common":[],"concerning":[],"preferred":[]},"compound_composition":[{"hq_id":"hq-c-org-000055","compound_name":null,"role":"chlorine_class_oxidizer","typical_concentration":"65-78% available chlorine as Ca(OCl)2; strong oxidizer (NFPA 3/0/1 OX); generates Cl2 gas on acid contact; ignites organics on contact"}],"identifiers":{"common_names":["swimming pool shock treatment — calcium hypochlorite (super-chlorination, chlorine gas release, fire hazard, chemical incompatibility)"],"aliases":[],"manufacturer":null,"brands":[]},"brand_examples":[],"brand_examples_disclaimer":null,"sources":[{"type":"expert_curation","name":"ALETHEIA Safety Database","date":"2026-03-26"}],"meta":{"schema_version":"4.0.0","last_updated":"2026-03-26","timestamp":"2026-05-14T01:27:44.975Z"}}