Fire Sealants Compared: FireMastic-300 vs FireMastic-HPE vs FireSilicone-EMA
Understanding the differences between these fire-sealing products helps you pick the right tool for each project. Below is a breakdown of how each performs — and when one might suit your needs better than the others.
Quick Comparison Table
| Product | Primary Purpose | Fire Rating | Joint / Gap / Penetration Types | Movement Tolerance & Flexibility | Best Use Cases |
|---|---|---|---|---|---|
FireMastic-300™ | Acrylic fire rated sealant for sealing linear gaps, fire rated wall systems, and metallic service penetrations | Up to ~5 hours | Linear gaps seals up to 50mm wide in a variety of substrates. Small cable bundles, and steel, copper & iron pipe penetrations. | High movement tolerance (± ~25%). | Internal walls/ceilings, partitions, linear gaps seals, metallic pipes penetrations and small electrical penetrations. |
FireMastic-HPE™ | High-pressure intumescent mastic for sealing combustible penetrations including large cable bundles, large combustible pipes, and HVAC services and A/C paircoil bundles. | Up to ~4 hours | Larger electrical cable bundles, & common combustible pipes such PEX, PEX AL, cPVC & uPVC. Huge range of HVAC solutions for lagged copper, a/c paircoil bundles and many mixed service bundles. | Expands under heat/pressure — ideal to seal voids that are left by melting combustibles in a fire scenario. | Versatile sealant for combustible electrical, plumbing and HVAC service penetrations. |
FireSilicone-EMA™ | Neutral-cure silicone sealant for flexible gap sealing, joints and external service penetrations, or wet areas such as bathrooms. | Up to ~4 hours | Wider linear gaps and control joints (up to ~100 mm), expansion joints, and electrical and metallic pipe service penetrations. (Such as brass lugged elbows in wet areas). | High movement tolerance (± ~25%) for linear gaps seals. High elasticity as recently proven with FyreBox™ testing. | Linear gap seals, expansion or control joints, exterior service penetrations or wet areas. |
What Sets Each Product Apart
FireMastic-300: The All-Rounder Sealant
- Best suited to sealing internal joints, partitions, linear gaps, small cable bundles or metallic pipe penetrations.
- Strong fire resistance and good acoustic performance make it valuable in apartments, offices or any space needing combined fire and sound control.
- Acrylic base and easy tooling give installers a familiar, clean, paintable finish. Offers sprinkler pipe testing without need for thermal wraps or blankets.
Use it when: You’re sealing regular joints or metallic service penetrations in internal walls or ceilings; need both fire and acoustic separation; and want a simple, paintable finish at a cost effective solution. Used on conjunction with many other BOSS Fire firestopping products and systems.
FireMastic-HPE: The High-Pressure Penetration Specialist
- High pressure exerting intumescent sealant engineered for scenarios with larger combustible service penetrations and mixed services bundles that melt and deform under fire.
- Expands up to 40x under heat to seal around combustible pipes, conduits, larger cable bundles and a wide range of HVAC services — especially useful for complex penetrations needing one sided application or remedial systems with BOSS Batts.
- Offers extensive versatility due to huge array of tested services and substrates for a wide range of trades.
Use it when: You need reliable fire sealing around electrical, plumbing, fire or HVAC service penetrations in new build or retrofit applications. You’re looking for one sealant that will do more applications.
FireSilicone-EMA: The Flexible, All-Weather Sealant
- Highly flexible, suitable for large joints, expansion joints, external applications, wet areas or where UV protection is required.
- Seals large linear gaps that offers significant elasticity and flexibility. Accommodates movement and remains weatherproof — ideal for external or exposed joints.
- Also suitable for a variety of metallic service penetrations such as brass lugged elbows in wet areas, or steel, copper & iron pipes or smaller cable penetrations.
- Recently tested in conjunction with the BOSS FyreBox™ for seismic movement as an airtight smoke seal.
Use it when: You’re sealing external joints, or wet areas, or joints where movement, weather exposure or width exceed limits for standard mastics. Also suitable for some metallic service penetrations needing a flexible, durable finish.
How to Choose: Matching Product to Project Needs
- Need fire + acoustic sealing for internal partitions or penetrations? Go with FireMastic-300™.
- Dealing with mixed service penetrations or plastic pipes? Use FireMastic-HPE™ for a more robust, heat-resistant seal.
- Working with external joints, or wet areas? Choose FireSilicone-EMA™ for flexibility and weather-resistance.
Also consider future maintenance, environmental exposure, joint movement and type of services passing through a penetration. The right sealant installation easier and reduces risk of non-compliance.
Summary
Each of these BOSS fire-sealants has a role. None is “better” in all cases — the strength comes from choosing the right one for the job.
- FireMastic-300™ is a flexible generalist for internal fire and sound partitions and metallic pipes and cables.
- FireMastic-HPE is a heavier-duty solution for combustible services penetrations, mixed HVAC bundles and larger cable bundles with more versatility for service penetrations.
- FireSilicone-EMA is the flexible, weather-proof option for joints, external work and wet areas.
Use this guide to help you specify the right solution — for safety, compliance and long-term reliability.
Want to Know More?
BOSS Fire can provide full technical guidance, installation details and project support. Get in touch if you would like help selecting the right fire stopping system for your build.
