Safe fire ratings indicate how long a safe can protect its contents from extreme heat during a fire.
Fire-resistant safes are designed and tested to withstand specific external temperatures for a set amount of time, ensuring that the internal temperature remains below a level that would damage the contents, particularly paper documents.
Understanding Fire Safe Ratings
A fire rating is typically expressed as a time duration at a specific external temperature. For example, a rating might be "60 minutes at 1,200°F". This rating isn't about preventing the safe from getting hot, but rather about controlling how hot it gets inside and for how long.
The critical factor for most contents, especially paper documents, is preventing the internal temperature from reaching a point where they will char or ignite. Paper typically begins to char around 400°F (204°C) and can ignite around 450°F (232°C). Therefore, fire safes designed for paper documents are tested to keep the internal temperature below a certain threshold, commonly 350°F (177°C).
As an example, a safe rated for 60 minutes at 1,200° F means that if you were to have a 1,200° fire for 60 minutes, the inside of the safe stays below 350° for at least a 60 minute period during a normal house fire.
Key Elements of a Fire Rating
- Duration: The length of time the safe was exposed to high temperatures during the test (e.g., 30 minutes, 60 minutes, 120 minutes).
- External Temperature: The maximum temperature the external environment reached during the test (commonly 1,200°F or 1,700°F). This simulates the conditions of a severe fire.
- Internal Temperature Limit: The maximum temperature the inside of the safe is allowed to reach during the test while still receiving the rating (typically 350°F for paper).
How Testing Works
Independent testing laboratories, such as Underwriters Laboratories (UL) or ETL (Intertek), perform standardized tests to verify a safe's fire resistance. During testing:
- The safe is placed in a furnace and heated rapidly to the specified external temperature.
- The safe remains in the furnace at or above that temperature for the rated duration.
- Internal temperatures are monitored throughout the test.
- After the heat exposure, the safe is often subjected to a "drop test" (simulating falling through a burning building) followed by re-heating to test its structural integrity under fire conditions.
- A safe passes if the internal temperature never exceeds the threshold (e.g., 350°F for paper) throughout the heating and cool-down period, and if the safe remains structurally sound and locked.
Ratings for Different Contents
While 350°F is suitable for paper, other valuables are more sensitive to heat:
- Digital Media: Items like hard drives, USB drives, CDs, and photographs are damaged at much lower temperatures, often around 120°F to 150°F (49°C to 66°C). Safes specifically designed for media protection have ratings with a lower internal temperature limit, like 125°F (52°C).
When choosing a safe, consider what you need to protect and select a rating that keeps the internal temperature below the damage threshold for those specific items.
Example Fire Ratings
| Rating | External Temp. | Duration | Internal Temp. Limit (Typical for Paper) | Purpose |
|---|---|---|---|---|
| UL 72 Class 350 - 1 Hr | Up to 1700°F (927°C) | 60 mins | Below 350°F (177°C) | Protects paper documents |
| UL 72 Class 350 - 2 Hr | Up to 1700°F (927°C) | 120 mins | Below 350°F (177°C) | Longer protection for paper documents |
| UL 72 Class 125 - 1 Hr | Varies (lower temp) | 60 mins | Below 125°F (52°C) | Protects digital media, photos, negatives |
| ETL Verified | Varies (often 1200°F) | 30/60 mins | Below 350°F or 125°F | Similar protection based on test specifics |
Understanding these ratings helps ensure that the safe provides adequate protection for your specific valuables in the event of a fire.
