For Architects & Design Professionals
Specify With Confidence.
The Brass-Seal is among the first mail slots independently verified under ASTM E283 by Intertek. The same standard applied to windows and doors. Now available for specification.
ASTM E283 Tested.
Independently Verified.
The Brass-Seal Forged Brass Mail Slot was tested at Intertek's facility in Fresno, California under ASTM E283/E283M-19 - the Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Skylights, Curtain Walls, and Doors Under Specified Pressure Differences. It is among the first mail slots to undergo this standard.
Results are third-party verified and available in full upon request. The report may be included in specification packages, submitted for energy compliance documentation, and used to support utility rebate applications.
| Configuration | Test | Result | Allowable Max | Status |
|---|---|---|---|---|
| Interior (standalone) | Air Infiltration · 75 Pa | 0.6 L/s/m² (0.12 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
| Interior (standalone) | Air Exfiltration · 75 Pa | 0.3 L/s/m² (0.06 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
| Exterior (standalone) | Air Infiltration · 75 Pa | 1.0 L/s/m² (0.20 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
| Exterior (standalone) | Air Exfiltration · 75 Pa | 0.6 L/s/m² (0.11 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
| Paired System | Air Infiltration · 75 Pa | 1.0 L/s/m² (0.20 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
| Paired System | Air Exfiltration · 75 Pa | 0.6 L/s/m² (0.11 cfm/ft²) | 1.5 L/s/m² (0.3 cfm/ft²) | PASS |
Intertek Building & Construction · Report No. T4376.01-301-44-R1 · April 2026 · Test pressure: 75 Pa (1.57 psf) · Full report available upon request at info@blockouttheair.com
Built for the Specification Channel.
Mail slots are commonly noted in energy audits and blower door tests as significant air leakage points. Until now, no verified product existed to address them within a specification context. The Brass-Seal fills that gap.
Available in exterior and interior configurations. The interior Brass-Seal preserves existing historic door hardware while sealing the building envelope from the inside.
Download Spec Section- ASTM E283 Verified - Full Intertek test report available. Report No. T4376.01-301-44-R1.
- Historic Preservation Compatible - The Brass-Seal Interior preserves existing exterior hardware. No demolition or construction waste.
- Two Configurations - Brass-Seal Exterior for new construction and full replacement. Brass-Seal Interior for retrofit and historic applications.
- Two Sizes - Letter (8.00" × 2.25" opening) and Magazine (11.375" × 2.50" opening).
- Energy Documentation - Savings estimates generated by ZIP code. Formatted for utility rebate submission.
- Patent Pending - Brass-Seal system. Mail Slot Insulator carries two granted utility patents.
- London Design Award - Gold, 2024. Mail Slot Insulator.
T4376.01-301-44-R1
ASTM E283/E283M-19 · Intertek Building & Construction · Fresno, California · April 2026 · Full report available upon request at info@blockouttheair.com.
Specification &
Drawing Package.
All documents are available for direct download. Engineering drawings are provided in PDF, Revit Family (.rfa), and STEP formats. The CSI MasterFormat Division 08 specification section is formatted for direct inclusion in project packages. For custom format requests or the full Intertek test report, contact info@blockouttheair.com.
| Document | Letter Size | Magazine Size |
|---|---|---|
| Engineering Drawing | Download PDF | Download PDF |
| Revit Family (.rfa) | Download RFA | Download RFA |
| 3D Model (.step) | Download STEP | Download STEP |
| Drill Template | Download PDF | Download PDF |
| CSI Spec Section 08 71 13 | Download PDF | |
Intertek ASTM E283 Report No. T4376.01-301-44-R1 available upon request · info@blockouttheair.com
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