A dry ice bag does not leak meltwater. Dry ice sublimates straight to CO₂ gas, so any “wet” you see on a dry ice bag or carton is condensation from humid air, or frost thawing as the surface warms. You can stop it with insulation, a vapor barrier, smart label placement, and safe venting that meets 2025 rules.
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Why “sweat” happens: Dew point physics for a dry ice bag in real warehouses and vans
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How to stop drips: A 6‑step pack‑out that keeps a dry ice bag dry on the outside
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Sizing the refrigerant: How much dry ice a dry ice bag needs for 24–72 h lanes
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Safety & compliance: UN1845, IATA PI 954 (2025), and why venting a dry ice bag is mandatory
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Dry vs. gel: When a dry ice bag beats gel packs—and when gels are smarter
Why does a dry ice bag “sweat” instead of leak water?
Core answer: A dry ice bag never makes liquid water; it makes CO₂ gas. The “sweat” is moisture from the air condensing on a surface colder than the dew point, or frost that later thaws. Think of a cold soda can on a humid day—same physics, colder surface.
What’s going on: When warehouse or last‑mile air hits a dry ice bag that is far below freezing, the outer film or carton sits under the local dew point. Water vapor becomes droplets or frost on that cold surface. As the route progresses and the surface warms, frost turns to visible water. Your dry ice bag didn’t leak; the air did. Use insulation to keep the outer surface warmer than the dew point, and add a vapor barrier to shield fiberboard.
Dew‑point thresholds for a dry ice bag
What to watch, at a glance
| Factor | Typical value | What it means | For you |
|---|---|---|---|
| Ambient temperature | 23 °C / 73 °F | Warm air carries more moisture | Higher sweat potential |
| Relative humidity | 60–75% | Higher RH → higher dew point | Plan barriers/absorbents |
| Dew point | 15–20 °C | Condensation threshold | Keep outer wall ≥ dew point |
| Outer carton surface | 5–15 °C | Below dew point in most lanes | Expect “sweat” without fixes |
Practical tips
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Warm the outside, not the payload: Add insulation or a foil/PE liner so the outer wall of the dry ice bag stays at/above the dew point.
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Move paperwork: Put labels on a warm sleeve or second carton panel, away from cold spots on the dry ice bag.
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Limit humid air exchange: Pack fast in a cooled room; keep doors shut on muggy docks.
Field case: A seafood shipper saw soaked labels in summer. After adding a foil‑laminated liner + double‑wall carton to warm the surface and moving labels to a sleeve, “wet box” complaints fell near zero with no temperature excursions.
Will a dry ice bag leak water inside the box?
Short answer: No—any interior moisture is from humid air that got in, or frost that later thawed. Add a vapor‑tight inner liner, but keep the outer package vented so CO₂ from the dry ice bag can escape safely.
Causes of interior “wet”: Air exchange during handling, damp product packaging, and cold inner films sitting below dew point. A sealed dry ice bag is not the culprit; sealing is unsafe and non‑compliant anyway. Use a vapor barrier to trap cold at the core and protect fiberboard from moisture ingress.
Pack‑out steps to stop a dry ice bag from “sweating”
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Pre‑condition shipper in a cool, dry room (30–60 min).
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Load dry ice into a dry ice bag; cinch, don’t hermetically seal.
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Insert into a foil/PE vapor barrier; close the liner at the top.
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Use adequate insulation (EPS/EPP/VIP or high‑R paper liners).
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Place labels on a warm sleeve or secondary outer carton.
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Vent safely—packages must not be airtight (UN1845, IATA PI 954).
How it helps: The inner barrier reduces moisture ingress; more insulation keeps the outer wall above the dew point; venting from the dry ice bag prevents pressure and keeps performance consistent.
How much dry ice should a dry ice bag carry to avoid over‑cooling the outer wall?
Rule of thumb: Plan ~5–10 lb per 24 h depending on insulation and lane heat load. More mass holds temperature longer but can drop the carton surface further below the dew point if insulation is thin. Balance dose, insulation, and dwell time.
Quick estimator for a dry ice bag (copy/paste)
Validate with a small A/B test and data loggers; adjust for summer/winter lanes.
3‑step self‑check (engagement tool)
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Is your packing room ≤20 °C and RH under control?
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Is the outer wall of the dry ice bag likely ≥ local dew point?
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Are vents unobstructed and labels placed on a warm sleeve?
Is a dry ice bag safe and compliant in 2025 (UN1845, IATA PI 954)?
Yes—if it’s vented and marked. Dry ice bag shipments must permit CO₂ to escape, carry UN1845 marks, and declare net dry‑ice mass. Do not make the package airtight. Worker safety: ventilate vehicles and rooms; follow exposure guidance.
Key notes for 2025:
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Venting required: Never seal a dry ice bag airtight.
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Marking: “Dry ice / Carbon dioxide, solid,” UN1845, and net mass (kg).
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Air acceptance: Follow IATA DGR 66th Edition (PI 954).
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Safety: Handle dry ice bag with gloves; ventilate to avoid CO₂ buildup.
Dry ice bag vs gel packs—when does water really matter?
If zero free water at delivery is critical, a dry ice bag wins. It generates no meltwater. For 2–8 °C lanes, sweat‑proof gels are often simpler with fewer hazmat steps. Combine wisely if you use both.
| Use case | Dry ice bag | Gel packs | What to do |
|---|---|---|---|
| Frozen foods (≤ −18 °C) | Long hold, no meltwater | Can create condensation as they warm | Prefer dry ice + barrier |
| Chilled 2–8 °C | Over‑cool risk | Tunable and non‑hazmat | Prefer sweat‑proof gels/PCMs |
| Label integrity | Needs condensation control | Needs absorbent control | Use label sleeve + barrier |
| Air compliance | UN1845 rules apply | Not dangerous goods | Choose based on temp target |
Practical scenario: Switching to a dry ice bag with a foil liner and label sleeve cut “wet box” claims by >80% in 2‑day lanes, with compliance ≥99%.
2025 trends that make a dry ice bag drier and smarter
What’s new: Reusable VIP shippers that keep outer walls warm, PFAS‑free paper liners with better barrier performance, and broader use of IoT loggers for temp/RH/CO₂. These reduce condensation windows and waste while supporting sustainability goals.
Latest at a glance
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Reusable/VIP expansion: Warmer outer surfaces for the same payload window
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Barrier upgrades: Foil/PE and next‑gen papers replace legacy coatings
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Smarter ops: Lane analytics + self‑checks standardize dry ice bag success
Market insight: Cold‑chain packaging grows steadily on biologics and e‑grocery volumes; hybrid PCM + dry ice bag strategies right‑size dose and cut moisture‑related claims.
FAQs
Does a dry ice bag sweat or leak water?
No. Dry ice sublimates to CO₂ gas. “Sweat” is condensation or thawed frost on cold surfaces. Control dew point exposure with insulation and a vapor barrier.
Why was my carton wet after using a dry ice bag?
Fiberboard absorbs condensation when its surface sits below the dew point. Add a foil/PE liner, use dual absorbent pads, and move labels to a warm sleeve.
How much dry ice for 48 h?
Typically 12–16 lb in quality EPS; more for thin foam or hotter lanes. Validate with data loggers before scaling.
Can I seal a dry ice bag to reduce moisture?
No. Packages must vent gas by rule. Hermetic sealing is unsafe and non‑compliant. Use internal vapor barriers instead.
Summary & Recommendations
Key points: A dry ice bag doesn’t make water; the air does. Keep outer surfaces above the dew point with insulation and a vapor barrier, place labels on a warm sleeve, and keep packages vented and marked per UN1845/IATA PI 954. Plan ~5–10 lb per 24 h and validate by lane.
Next steps (CTA):
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Run a 2‑box A/B this week: current vs. foil/PE barrier + sleeve.
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Log temp/RH/CO₂ on one high‑humidity lane.
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Standardize a 6‑step dry ice bag pack‑out in your SOPs.
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Talk to Tempk for a lane‑specific “no‑sweat” pack‑out template.
About Tempk
We are a cold‑chain packaging and analytics team focused on dry ice, PCMs, and compliant shippers. We pair validated EPS/VIP systems with practical moisture control—barriers, absorbents, and process checks—so your dry ice bag shipments arrive dry and on‑spec. Typical outcomes: >80% fewer wet‑box complaints and measurable cost savings from right‑sized refrigerant loads.
Ready for a dry, compliant pack‑out? Request a dry ice bag audit and validation plan today.
