What is Thermal Blankets and Bivy Sacks?
Thermal blankets are thin, metallic sheets that reflect body heat back to the user while blocking wind. Bivy sacks are waterproof bags that enclose the entire body, trapping heat and protecting from wind and water.
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What it is
Thermal blankets are thin, metallic sheets that reflect body heat back to the user while blocking wind. Bivy sacks are waterproof bags that enclose the entire body, trapping heat and protecting from wind and water. Both are compact, lightweight emergency insulation designed for survival situations, particularly when treating exposure.
What it does
These items prevent or treat hypothermia by conserving body heat in emergency situations. Thermal blankets reflect radiated body heat back to the user, dramatically slowing heat loss. Bivy sacks create a protected microenvironment around the body, blocking wind and water while trapping warm air. They work when conventional blankets are soaked or unavailable.
Why it matters
Hypothermia is a leading cause of death in marine emergencies and can set in quickly even in temperate conditions when combined with wind, water, and exhaustion. Cold water is considered any water below 70°F/21°C. Body heat loss can be rapid, especially if clothing is wet. Thermal blankets and bivy sacks are lightweight and compact enough to have in grab bags.
General Maintenance
Inspect thermal blankets and bivy sacks at the beginning of each sailing season and before a long voyage. . Check for tears, holes, or degraded areas in the material, verify packaging remains sealed if still in original packaging, ensure items haven't become brittle from age or temperature extremes, confirm they're stored in multiple accessible locations (grab bag, deck locker, life raft), replace any that show significant wear, and include several in any grab bags or life rafts. These items are inexpensive and have good shelf life, so maintaining adequate numbers is more important than trying to extend the life of degraded items.
Common Issues
- Material torn or punctured from sharp objects during storage
- Mylar blankets becoming brittle from age or temperature extremes
- Items stored in single location rather than distributed for emergencies
- Crew unfamiliar with proper use to maximize effectiveness
- Insufficient quantity for all crew members
- Materials degraded from chemical exposure in storage
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