FM 4950 Requirements for Welding Blankets, Curtains & Pads

Welding, cutting, grinding, heat treating, and other hot work operations can generate sparks, flames, molten metal, slag, and intense radiant heat. Without appropriate barriers, these ignition sources can reach nearby equipment, combustible materials, and other areas of a facility.

Welding curtains, blankets, and pads provide localized protection against these hazards. But selecting the right material requires more than looking at a fabric's temperature rating or weight.

FM 4950 establishes performance and certification requirements for welding pads, blankets, and curtains used during hot work operations. The standard evaluates products according to how they are positioned and the severity of the exposure they are expected to withstand.

For engineers, safety managers, welding supervisors, and procurement teams, understanding these categories is an important part of specifying the appropriate hot work protection.

What Is FM 4950?

ANSI/FM 4950 is the American National Standard for evaluating welding blankets, pads, and curtains for hot work operations.

The standard is designed to evaluate whether these products can help prevent ignition of combustibles during welding, cutting, and related operations. The evaluation considers factors such as flame propagation, burn-through, temperature transmission, charring, and, in applicable cases, performance after accelerated weathering.

Importantly, FM 4950 is not simply a temperature-rating standard.

A fabric that can withstand a particular continuous or peak temperature is not automatically appropriate for every welding application. Hot work protection depends on the combination of:

• Exposure severity

• Product orientation

• Spark and molten-metal exposure

• Heat transfer through the material

• Fabric construction

• Coating or treatment

• Mechanical integrity after exposure

• The condition of the finished product

The 2024 FM 4950 standard also addresses certification considerations beyond laboratory performance, including product marking, manufacturing quality, and surveillance.

Three FM 4950 Performance Categories

Typical applications include:

• Welding-area partitions

• Welding drapes

• Grinding and chipping areas

• Light welding operations

• Heat-treating operations

• Sandblasting areas

• Shipbuilding and ship repair

A welding curtain must resist melting, burning, burn-through, and deformation under the applicable exposure while maintaining the flexibility and dimensional stability required for vertical installation.

Key point: A material intended only for curtain service should not automatically be treated as suitable for horizontal blanket or pad applications.

3. Welding Pads

Welding pads are intended for horizontal applications involving severe exposure.

They are positioned directly beneath operations that can generate substantial quantities of molten material or intense heat, including heavy welding and cutting operations.

Typical applications include:

• Heavy welding

• Oxy-fuel cutting

• Molten metal exposure

• Severe slag exposure

• Metal fabrication and processing

The welding pad category has the most demanding exposure conditions of the three categories. Under the fire and thermal resistance requirements, a qualifying pad must resist burn-through and limit heat transmission to the underside. For welding pads, the temperature on the underside must not exceed 500°F (260°C) during the test.

Can a Welding Pad Also Be Used as a Blanket or Curtain?

Yes. A welding pad is designed for more severe horizontal exposure than a welding blanket or curtain. Because of this higher level of protection, an FM 4950-approved welding pad can also be used for applications that require a welding blanket or curtain, provided the product is suitable for the intended installation.

Always check the product's FM 4950 classification, intended orientation, and manufacturer's instructions before using it in a different application.

What Does FM 4950 Test?

FM 4950 evaluates more than whether a fabric remains intact when exposed to heat. The standard uses several tests to assess the finished material's ability to provide protection during hot work.

1. Fire and Thermal Resistance

Evaluates how well the product resists flame spread, burn-through, and heat transfer during hot work exposure. Horizontal products are tested for their ability to protect materials beneath them, while curtains are tested in a vertical position. A fabric's continuous operating temperature alone does not determine its performance against sparks, molten slag, or cutting heat.

2. Paper Ignition Test

The paper ignition test evaluates whether heat and flame passing through a horizontal welding pad or blanket can ignite combustible material beneath the product. This provides a practical measure of the material's ability to protect the area on the unexposed side during the specified hot work exposure.

3. Charring and Embrittlement

Some heat-resistant fabrics can retain their overall shape after exposure while becoming brittle in the charred area.

FM 4950 therefore evaluates the condition of exposed material after testing to determine whether charring has compromised its structural integrity. For welding pads and blankets, this helps address the durability of the material after severe thermal exposure.

This is particularly relevant for reusable welding protection that must be folded, moved, installed, and stored repeatedly.

4. Accelerated Weathering

Outdoor and partially enclosed hot work areas can expose welding protection to ultraviolet radiation and moisture.

FM 4950 includes accelerated weathering evaluation for applicable products. Earlier versions of the standard specify exposure to ultraviolet radiation and water before subsequent performance testing.

For applications such as shipyards, construction, and outdoor industrial maintenance, weathering resistance can be an important part of material selection.

Choosing the Right Fabrics for FM 4950 Applications

Note: We do not currently certify our materials to FM 4950 due to the high cost of the certification process. However, our materials meet or exceed the applicable FM 4950 performance requirements for their intended applications. If FM 4950 certification is required for insurance purposes, we can pursue certification when the material volume and project value warrant the associated expense. Contact us to discuss your application and certification requirements. 

Inspection and Maintenance of Welding Materials

Even a properly selected welding blanket, curtain, or pad can become unsuitable for service if it is damaged or contaminated.

Inspect protective textiles for:

• Holes or burn-through

• Severe charring

• Cracked or embrittled areas

• Fraying

• Torn seams

• Damaged grommets or attachment points

• Oil or chemical contamination

• Loss of coating

• Excessive abrasion

Remove damaged material from service when its condition could compromise the protection required for the application.

Cleaning procedures should follow the manufacturer's instructions for the specific fabric or finished product. Do not assume that industrial laundering is suitable for every coated or treated high-temperature textile.

Does FM 4950 Replace NFPA 51B Hot Work Procedures

No.

FM 4950 evaluates the performance of welding pads, blankets, and curtains. It does not replace the broader hot work controls required by applicable safety procedures.

NFPA 51B addresses fire prevention during welding, cutting, and other hot work. Protective covers are one part of a broader hot work safety program that can also include combustible-material control, permits, fire watches, area preparation, and post-work monitoring.

A compliant hot work program should therefore address both material selection and work-practice controls.

Related Articles:

What Has Changed in NFPA 1970 Firefighting PPE Standards

How to Choose ISO 11612-Compliant Safety Apparel

ASTM & ISO Test Standards for High-Temperature Fabrics

Conclusion

FM 4950 provides a framework for evaluating welding curtains, blankets, and pads according to their intended orientation and exposure severity. For buyers and safety professionals, the most important steps are to identify the hot work hazard, select the appropriate performance category, review the complete material construction, and verify the documentation for the finished product.