Invert Heat Packs

Invert Heat Packs are single-use warming packs designed for shipping live invertebrates during cold weather. They provide over 40 hours of heat, helping to keep isopods, springtails, and other invertebrates at safe temperatures during transit when ambient temperatures drop.

What It Is

A 40+ hour heat pack—the same type used by invertebrate suppliers across the UK for shipping tarantulas, isopods, mantids, and other temperature-sensitive animals. The pack activates when exposed to air and generates steady warmth for the duration of most next-day delivery timescales.

The ones we personally use and sell are from the UKs largest Invert seller (to my knowledge) The Spider Shop. So this product is used by them thousands of times per year directly as well as the backbone to winter shipping to probably hundreds of other invert hobbiests/businesses.

When You Need One

Heat packs are recommended during colder months, typically October through March in the UK, when overnight temperatures can drop low enough to harm invertebrates in transit.

Add a heat pack to your order when:

• Overnight temperatures at your location or the sender's location fall below 5°C
• You're ordering tropical species that are particularly cold-sensitive
• Weather forecasts suggest cold snaps during the delivery window
• You want extra peace of mind during marginal conditions

You probably don't need one when:

• Summer months with reliably warm overnight temperatures
• Ordering hardy temperate species during mild weather
• Local collection rather than postal delivery

Important Guidelines

Temperature limits: Heat packs may stop generating heat if exposed to freezing conditions (below 0°C). Even with a heat pack, avoid shipping when overnight temperatures are forecast below 5°C. The pack helps but isn't magic—it can't overcome genuinely freezing conditions.

Use one per box: A single heat pack is sufficient for standard shipping boxes. Using multiple packs risks overheating the animals, which can be just as harmful as cold.

Never place animals in direct contact: The heat pack should be wrapped or positioned so animals aren't sitting directly on or against it. Direct contact can cause heat stress or burns. Typically, suppliers wrap the heat pack in newspaper or place it in a separate section of the packaging.

Check both locations: Weather can vary significantly between the sender's location and yours. Check forecasts for both postcodes before ordering in borderline conditions.

Consider other factors: Bank holidays, postal strikes, severe weather warnings, or anything that might delay delivery increases cold exposure risk. If conditions look questionable, delay the order.

How PostPods Uses Heat Packs

PostPods ships Monday to Thursday using Royal Mail next-day service. During cold months, we add a heat pack to your order helps protect your isopods during the overnight and delivery period. The pack is activated and placed in the shipping box before dispatch.

Cost and Value

At £1.49, heat packs are inexpensive insurance. Given that we (as a hobby) often post inverts in the post, adding one during winter months makes straightforward sense as it protects our animals on the way to their new homes. 

Limitations

Heat packs are helpful but have limits:

• They work best above freezing—below 0°C they may fail
• They can't compensate for extended delays in freezing conditions
• They require proper positioning (not touching animals directly)
• They're single-use and cannot be reactivated

Who Should Buy These

Recommended for:

• Any winter orders (October–March)
• Tropical species orders year-round in colder regions
• Customers in Scotland, northern England, or other areas with colder overnight temperatures
• Anyone who wants peace of mind during marginal weather

Optional for:

• Summer orders in mild conditions
• Hardy European species during moderate weather
• Very short transit times in warm conditions