How to Use Reusable Dry Ice Packs in 2025

Updated: September 2, 2025. If you ship frozen goods, reusable dry ice packs can cut hazards, cost, and complexity. They hold steady at sub‑zero targets without CO₂ off‑gassing, avoid UN1845 labels, and fit −15 °C to −25 °C lanes. Below you’ll learn how they work, how to size them, what rules apply, and where dry ice still wins.

• What are reusable dry ice packs and how do they work? Sub‑zero PCMs explained for frozen shipping −20 °C/−25 °C.

• When should you choose reusable dry ice packs vs. dry ice? Decision matrix for PCM vs dry ice lanes.

• How do you size and condition packs correctly? A copy‑and‑paste how to size PCM for frozen checklist and calculator.

• Are they air‑legal and what labels apply? Dry ice label UN1845 net kg vs. “no DG label” for PCMs.

• What changed in 2025? −21 °C/−25 °C trends and sustainability signals you can act on now.

What are reusable dry ice packs and why now?

Reusable dry ice packs are sub‑zero phase‑change gel packs that hold a steady −20 °C to −25 °C plateau through many freeze–thaw cycles. They’re non‑hazardous, can touch product, and don’t require UN1845/Class 9 labels because they are not dry ice. Freeze them to their stated melt point (e.g., −25 °C for −25 °C packs) to unlock full capacity.

Think of each pack as a rechargeable “cold battery.” You “charge” it to its melt point; as it absorbs heat, it melts at that temperature, keeping your payload cold and predictable. That gives you frozen control without dry ice’s venting and paperwork—ideal for diagnostics, frozen foods, and specialty pharma that target < −15 °C or < −20 °C.

Which melt point fits your job (−20 °C vs −25 °C)?

Choose the melt point by spec and route. −20 °C packs suit “keep < −15 °C” lanes; −25 °C adds headroom for “keep < −20 °C.” Dry ice (−78.5 °C) is still the tool for ultra‑cold or multi‑day holds. Always charge to melt point—−18 °C freezers won’t fully charge −25 °C packs.

Practical tips and cautions

• Match melt point to lane to avoid over‑ or under‑cooling.

• Charge fully to the actual melt point; partial charges shorten hold time.

• Simplify labels: PCMs need no UN1845/Class 9 marks in air cargo.

Field case: A diagnostics lab swapped dry ice for −25 °C PCMs on overnights and held < −20 °C through morning pickups, with fewer carrier refusals and no DG handling.

How to size and condition reusable dry ice packs?

Size by thermal load, not box size. Start with 1–1.2 kg of −25 °C PCM per 5 L payload per 24 h, then adjust for insulation and ambient heat. Freeze packs to melt point (e.g., −25 °C), pre‑chill product and shipper, and pack symmetrically with minimal air gaps.

You can picture your box as a leaky thermos—bigger boxes, hotter trucks, and lid openings “drain” your cold battery faster. Pre‑chilling shrinks day‑one losses; a fully charged −25 °C pack absorbs heat at −25 °C until it’s melted, giving you a flat, predictable profile.

Baseline per 24 h: −20 °C PCM = 1.0 kg / 5 L; −25 °C PCM = 1.2 kg / 5 L.
Formula: PCM kg = Baseline × (Duration/24) × Insulation × Ambient × (Payload L/5)
Tip: place a logger near product core and validate on your lane before scaling.

Quick conditioning checklist

1. Confirm lane target and duration.

2. Pick −20 °C or −25 °C PCMs.

3. Freeze to the stated melt point.

4. Pre‑chill shipper & payload.

5. Pack symmetrically; fill voids.

6. Add logger; close and record charge state.

Real result: A meal‑kit brand replaced ~10 lb dry ice with four −25 °C bricks in a 20 L qualified shipper for 36 h routes, cutting DG steps and smoothing hub acceptance.

Are reusable dry ice packs allowed on flights—and what labels apply?

Yes. Reusable dry ice packs (PCMs) are not “dry ice,” so no UN1845/Class 9 marks are required. True dry ice needs proper shipping name, UN1845, net kg on the outer pack, and venting. Passengers with dry ice are capped at 2.5 kg with airline approval; packages must vent.

Do this in practice:

• For PCM shipments: mark normally; no DG declaration (check carrier house rules).

• For dry ice: use “Dry ice/Carbon dioxide, solid” + UN1845 + net kg; ensure venting; follow IATA/FAA job aids.

PCM −20 °C vs −25 °C: which melt point is right for reusable dry ice packs?

Choose based on spec, box size, and time. −20 °C works for “keep < −15 °C” and small, short lanes; −25 °C is better for “keep < −20 °C” or hotter ambients. Dry ice still covers ultra‑cold or long, bulky routes. For 2–8 °C meds, use +5 °C PCMs—not dry ice—to avoid freezing damage.

Decision matrix (fast pick)

2025 trends in reusable dry ice packs and cold chain

Trend overview: Sub‑zero PCMs (−20 °C/−25 °C) continue to expand as dry‑ice alternatives in 2025, with more biodegradable gels, −21 °C options in EU lanes, and sharpened dry‑ice acceptance checklists that push shippers toward PCMs where feasible. ROI improves as DG hassle decreases.

Latest progress at a glance

• Biodegradable −25 °C gels: modular panels for kit programs.

• −21 °C PCM adoption: frozen food/diagnostics in Europe.

• Policy clarity: UN1845/net‑kg/venting emphasized in 2025 checklists.

Market insight (plain English): PCMs don’t beat dry ice on sheer cold, but they often win on predictability, compliance, and customer experience for −15 °C to −25 °C lanes—especially where DG steps slow you down.

Pro tips and user scenarios

• Hot‑weather route: Use −25 °C packs on all sides, fill voids, add top panel; log at 5‑min intervals.

• Flight‑heavy lane: Prefer PCMs to avoid DG checks; if dry ice is required, label UN1845 + net kg and ensure venting.

• Refrigerated biologics: Use +5 °C PCMs with proper conditioning; never pair dry ice with 2–8 °C vaccines.

Practical example: Overnight diagnostics in a qualified shipper with −20 °C packs maintained < −15 °C through morning pickup without DG labels—handled like standard express.

Lane fit self‑test (engagement tool)

Score your lane; higher scores suggest moving toward dry ice or hybrid.

• Temperature target: < −20 °C (2); < −15 °C (1); 2–8 °C (0)

• Hold time: ≤ 36 h (1); 48–72 h (2); > 72 h (3)

• Payload size: ≤ 5 L (1); 6–20 L (2); > 20 L (3)

• Insulation: Qualified (1); Foam shipper (2); Soft tote (3)

• Air transport constraints: Avoid DG preferred (2); DG okay (0)

Rule of thumb: 5–7 = PCMs likely ideal; 8–10 = pilot both; 11–13 = dry ice/hybrid.

FAQ: reusable dry ice packs

Q1: Are reusable dry ice packs actually “dry ice”?
No. They are PCMs with defined melt points (e.g., −20 °C or −25 °C) and do not off‑gas CO₂ or require UN1845 labels.

Q2: What freezer do I need for −25 °C packs?
Use a commercial freezer capable of −25 °C or below; −18 °C won’t fully charge a −25 °C pack.

Q3: Can I fly with reusable dry ice packs?
Yes. They are not dry ice. For dry ice, FAA caps passengers at 2.5 kg with airline approval; packages must vent and be marked.

Q4: Do reusable packs work for 2–8 °C meds?
Use +5 °C PCMs; avoid dry ice/frozen gels to prevent freezing injury.

Q5: Are there −21 °C options?
Yes. −21 °C PCMs are common in EU packaging lines as dry‑ice substitutes. Match melt point to your spec.

Summary & recommendations

Reusable dry ice packs provide predictable frozen control for −15 °C to −25 °C lanes without DG labels or CO₂ hazards. Size by thermal load, charge to melt point, and validate with data logging. Keep dry ice for ultra‑cold or multi‑day holds, or use hybrids when needed. Action plan: map lanes, choose −20 °C/−25 °C PCMs, pilot two packouts with loggers, refine mass, and maintain a dry‑ice contingency for edge cases.

About Tempk

We’re a cold‑chain packaging and analytics team focused on validated, lane‑specific packouts. We pair qualified shippers with the right coolants—PCMs or dry ice—to hit your temperature targets with fewer touchpoints and lower landed cost. Strengths: evidence‑based SOPs and fast pilot‑to‑scale across DTC food, diagnostics, and specialty pharma. Ready to validate your lanes? Talk to a Tempk specialist for a free PCM vs. dry‑ice comparison.