How do they cremate a body?
Executive summary
Flame (retort) cremation heats the body in a sealed chamber to roughly 1,400–2,000°F until soft tissues are vaporized and only bone fragments remain; the active heating phase typically lasts 30 minutes to two hours and is followed by cooling and pulverization of bone into “ashes” that are returned to families [1] [2] [3]. Alternative methods — most notably alkaline hydrolysis (aqua or water cremation) — use heated water and alkali to reduce the body to bone ash with lower emissions and are legal and expanding in several states [4] [5].
1. How flame cremation actually works — intense heat in a retort
Flame cremation takes place inside a cremation retort: a fire‑resistant chamber that raises temperatures high enough to combust organic material. Primary combustion in the main chamber consumes soft tissues and container materials; gases produced then move to a secondary chamber for further combustion before exiting through the facility stack [3]. Industry guides state retort temperatures commonly run from about 1,400–1,600°F, with some consumer‑facing sources citing peak temperatures up to roughly 2,000°F; the heat level destroys most soft tissue and degrades DNA [3] [1].
2. Timing, cooling and what families receive
The active combustion phase varies by body size and equipment: sources report that cremation may take as little as 30 minutes and more typically up to two hours, followed by a cooling interval of about 30–60 minutes before remains are processed [2] [3]. After cooling, remaining bone fragments are mechanically processed (commonly called pulverization) into the granular “cremains” families receive [2] [3].
3. Legal and administrative steps before cremation
Providers cannot begin without paperwork: families generally must sign authorization forms and a cremation permit is commonly required at county level, often tied to the death certificate and, in some cases, medical examiner clearance [6] [7]. Identification protocols and consent requirements are standard across industry guides to ensure correct remains are returned [6] [7].
4. Direct cremation and the market shift
Direct cremation — the immediate cremation without funeral rites or viewing — is a growing, lower‑cost model in which the body is transported, cremated, and the ashes returned with no formal service; some industry players claim direct cremations now make up a large share of cases [8] [9]. Market data cited by trade outlets show steeply rising cremation rates (NFDA estimates cited in trade reporting put U.S. cremation at about 63.4% in 2025), which is reshaping funeral operations toward higher‑volume cremation services [10] [9] [11].
5. Alternatives to flame cremation — alkaline hydrolysis and “green” options
Alkaline hydrolysis (often branded “water cremation” or aquamation) dissolves the body using heated water and alkali, producing bone ash and fewer airborne emissions; several states have legalized it and adoption grew through 2025 [4]. Some operators advertise low‑ or no‑emission facilities powered by renewable electricity, signalling both commercial and environmental positioning in the market [5].
6. What cremation destroys (and what it doesn’t)
High cremation temperatures destroy most DNA and make post‑cremation extraction difficult; DNA begins degrading at about 800°F and retorts operate far above that range, so successful DNA recovery is unlikely though not universally impossible from some bone or tooth fragments [1]. Sources caution that pulverization further reduces recoverable material [1] [3].
7. Industry oversight, risks and where reporting flags trouble
Recent state audits and industry briefs highlight regulatory gaps — inconsistent inspections, licensing lapses, and recordkeeping weaknesses — which matter because cremation has become the dominant disposition method and creates concentrated risk if oversight is weak [10] [12]. Trade reporting explicitly urges watching state regulatory initiatives and transparency issues as the sector consolidates [12] [9].
Limitations and unanswered questions
Available sources outline the mechanics, timing, paperwork, and alternatives but do not provide a single standardized procedural checklist that applies across all jurisdictions; laws and required temperatures vary by state and operator [3] [7]. Sources do not detail every step of chain‑of‑custody protocols or the exact chemical formulations used in alkaline hydrolysis at specific facilities — not found in current reporting (available sources do not mention the precise chain‑of‑custody steps or proprietary formulations).