Written and maintained by CASRAI Editorial Board
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General product information only, not medical advice. This page does not give treatment instructions, temperatures or application times; follow the manufacturer’s instructions for use and your facility’s clinical protocols.
Short answer
A moist heat pack is, in US regulation, a device made of silica gel in a fabric container that retains an elevated temperature and provides moist heat therapy for body surfaces. FDA classifies it as Class I under 21 CFR 890.5730, and it is exempt from premarket notification. “Hydrocollator” usually names the water-heated unit that warms such packs, which is a separate item from the pack itself.
Definition and scope
The eCFR text of 21 CFR 890.5730 defines the device in one sentence: “a device intended for medical purposes that consists of silica gel in a fabric container used to retain an elevated temperature and that provides moist heat therapy for body surfaces.” Three points follow directly from that wording.
- The definition is about construction and intended use. Silica gel, a fabric container, heat retention and moist heat therapy for body surfaces are all in the text. The regulation says nothing about sizes, temperatures or heating methods.
- Class I (general controls). The regulation exempts the device from the premarket notification procedures in subpart E of part 807, subject to the limitations in 21 CFR 890.9. For background on what that exemption route means, see our guide to FDA 510(k) premarket notification and the wider device classification overview.
- Reduced quality-system scope. The same section exempts the device from the quality management system regulation in part 820, except for requirements concerning records and complaint files under 21 CFR 820.35.
FDA’s Total Product Life Cycle database lists the device under the name “pack, heat, moist”, product code IMA, regulation number 890.5730, device class 1.
How it is used in practice
The Centers for Medicare & Medicaid Services describes the hydrocollator arrangement in its Medicare Coverage Database reference article A52502 (heating pads and hydrocollator units). A hydrocollator unit (HCPCS E0225 and E0239) is a container that is filled with water and then heated. Bags of “silicone dioxide or other material” (CMS wording) are placed in the heated water, and the packs are applied over towels. The article describes the use as warming a body part before physical therapy. The CMS page does not state a temperature, and neither does this guide.
That description explains the vocabulary. In day-to-day clinic talk, “hydrocollator” can refer to the heater, to the pack or to the whole system, so a purchase request or inventory line that only says “hydrocollator” may not tell a supplier which item is needed. Our guide to athletic training room equipment shows the same phrasing in a facility equipment list, where a “hydrocollator unit with moist heat packs” appears as one line item.
Moist heat pack, hydrocollator unit and moist heating pad compared
The three items below are easy to confuse. Each row is drawn from one of the sources listed at the end of this page.
| Item | What the source says | Source |
|---|---|---|
| Moist heat pack | Silica gel in a fabric container that retains an elevated temperature and provides moist heat therapy for body surfaces. Class I, product code IMA. | 21 CFR 890.5730; FDA TPLC |
| Hydrocollator unit (E0225, E0239) | A container filled with water and then heated; bags of “silicone dioxide or other material” go in the heated water, and packs are applied over towels. | CMS article A52502 |
| Moist electric heating pad (E0215) | A flexible device with electric resistive elements that must absorb and retain liquid water, and water must be added to the device. A different device from a silica gel pack. | CMS article A52502 |
Where it matters for labs, clinics and supply decisions
Regulatory status you can verify
For a supply or quality reviewer, the product code and regulation number are the lookup keys. Searching FDA’s TPLC database for product code IMA or regulation 890.5730 returns the device record, its class and any recall records. Because the device is Class I and exempt from 510(k), a missing 510(k) number is expected for this device type.
Recall records
As of 2026-10-30, the FDA record for product code IMA lists one recall: Bruder Healthcare Company, LLC, Class II, posted March 22, 2024. This page does not characterise the cause. To understand what the classes mean, see FDA recall classification, Class I vs II vs III.
Equipment versus billing category
CMS considers hydrocollator units institutional equipment and states they are denied as statutorily noncovered under the Medicare coverage article. That is a coverage statement about the heater unit, not a statement about safety or quality.
Checklist for an inventory or supplier entry
- Does the line name the pack, the heating unit, or both?
- Is it a silica gel pack (FDA 890.5730) or an electric heating pad (a different device)?
- Can the product code and class be matched to the FDA TPLC record?
- Are the manufacturer’s instructions for use filed with the item for the people who will handle it?
For how heat and cold modalities are sorted in clinical settings, see the hot and cold therapy clinical selection guide.
Common misunderstandings
- “Hydrocollator” is not the FDA term. The FDA entry is “moist heat pack”; the CMS article uses “hydrocollator unit” for the water container. The two documents describe linked but different items.
- A moist electric heating pad is not a silica gel pack. CMS describes the electric version by its resistive elements and its requirement to retain water; the FDA definition of the pack has no electrical component.
- Class I does not mean no rules. General controls apply, and records and complaint-file requirements under 21 CFR 820.35 still apply.
FAQ
What is a moist heat pack?
Under 21 CFR 890.5730, it is a medical device of silica gel in a fabric container that retains an elevated temperature and provides moist heat therapy for body surfaces.
What is a hydrocollator pack?
The term is used for packs warmed in a hydrocollator unit, a water-filled container that is heated. CMS describes bags of “silicone dioxide or other material” placed in the heated water and applied over towels.
Is a moist heat pack an FDA-regulated device?
Yes. It is Class I (general controls), product code IMA, exempt from premarket notification.
Does a moist heat pack need a 510(k)?
No. 21 CFR 890.5730 exempts it from the premarket notification procedures, subject to the limitations in 21 CFR 890.9.
Sources
- eCFR, 21 CFR 890.5730 Moist heat pack: https://www.ecfr.gov/current/title-21/section-890.5730 (checked 2026-10-30)
- FDA Total Product Life Cycle, product code IMA: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfTPLC/tplc.cfm?id=IMA (checked 2026-10-30)
- CMS Medicare Coverage Database, article A52502 (heating pads and hydrocollator units): https://www.cms.gov/medicare-coverage-database/details/article-details.aspx?articleid=52502 (checked 2026-10-30)
