Reduced-Scale Test to Assess the Effect 

of Fire Barriers on the Combustion 

Behavior of Core Flammable Materials:

an Upholstery–Material Case Study

Mauro Zammarano

Fire Research Division, NIST, USA

Some of the data in this presentation hasn’t been through the NIST review process and 

should be considered experimental / draft results.
• Fire Barriers as alternative to 

Chemical FRs

• Cube Test: reduced scale test to 

assess the effect of Fire Barriers

• Case Study: Upholstered Furniture

Outline

CUBE TEST

2

- Full-scale test (Chair Mock-ups)

- Bench-scale to Full-scale Correlation
• California State [Assembly Bill No 2998, Sep 29, 2018]

bans the use of FR based on halogenated, organo-phosphorous, organo-nitrogen, 

nanoscale chemical, chemicals of high concern in children’s products, mattresses, 

or upholstered furniture

Why Fire Barriers? Severe Restrictions on FRs in USA

• CPSC recommends to refrain from intentionally 

adding nonpolymeric, organo-halogen FRs in:

o children’s products

o upholstered furniture (UF) sold for use in residences

o mattresses (and mattress pads)

o plastic casings surrounding electronics.

FIRE 

RETARDANT

?

3

• State of Maine first State banning all flame retardants in residential UF

https://www.mainelegislature.org/legis/bills/bills_128th/billtexts/HP013801.asp

STATE LEVEL:

FEDERAL LEVEL [CPSC Docket No. CPSC–2015–0022, Sept’17]
Polymeric Material

Fire Barriers: a Physical Approach to Flame Retardancy

Two-fold mechanisms of action of Fire Barriers:

(1) Limiting generation rate of flammable pyrolyzate (Heat Transfer)

(2) Limiting or controlling the rate and location at which pyrolyzates 

are released and able to burn (Mass Transfer)

4

Schematic Combustion Process

mሶ bottom

mሶ top

Fire Barrier

qሶtop

qሶbottom

POLYMER → Gaseous products + Liquid products 

POLYMER PYROLYSIS

(gaseous pyrolyzates) 

(gaseous & liquid pyrolyzates) 
NIST Cube Test (ASTM WK65005) 

5

qሶ mሶ

One-Dimensional 

Heat/Mass Transfer

The sample is intended 

to be a representative 

cross-section of an item

Sample dimensions:

100 mm × 100 mm ×

product thickness

Polymeric

Core

Material

Insulation

Fire Barrier

Fire Barrier

Metal 

Frame

Substrate

Cone Heater

What is it? Tool for the Cone Calorimeter to capture Mass Transfer and Heat Transfer 

phenomena through the top and bottom of the sample.

What is used for? Characterize the combustion behavior of a flammable core material in 

presence of fire barriers. 
Schematic Drawing

6

F

F
Case Study: Upholstered Furniture (UF) 

• 1 Polyurethane Foam (TB117-2013)

• 1 Cover Fabric (Polypropylene)

• 6 Fire Barriers compliant with 

California Assembly Bill No 2998

Reduced Scale Test 

(Cube Test)

Full-scale Test

(Chair Mock-ups)

C

o

r

r

e

l

a

t

i

o

n

Materials
Fabric Type Materials Density

g∙m-2

Air Perm. 

cm3∙s-1∙cm-2

B0 Cover fabric Polypropylene 340 ± 7 3.9 ± 0.3

B1 Nonwoven-bonded polyester RC**/PSA*(top), cotton (bottom) 239 ± 21 22.4 ± 1.4

B2 Woven E glass, no sizing 109 ± 4 9.2 ± 2.2

B3 Nonwoven, 5% RC** binder Oxidized polyacrylonitrile fibers 240 ± 22 7.1 ± 0.5

B4 Woven E glass, no sizing 50 ± 1 31.4 ± 4.6

B5 Woven, core spun yarns Para-amid fiber, fiberglass core 278 ± 3 2.7 ± 0.0

B6 Nonwoven, needle-punched **RC/PSA hybrid yarn, glass yarn* 275 ± 4 9.7 ± 0.7

*PSA : Polysilicic acid

**RC : Regenerated cellulose

Barrier Materials

Materials compliant with California Bill AB 2998

8

B1, B5, B6: UF Commercial Barriers

B2, B3, B4: Experimental Barriers
Chair Mock-ups

1000

25

1000 150

FRONT VIEW Back cushion (polyester fibers)

Armrest padding (TB117-2013 foam)

Seat cushion (TB117-2013 foam)

Armrest support (5 mm plywood)

950 

300

SIDE VIEW

7 chair types (C0 to C6):

C0: cover fabric (B0) only

C1 to C6: cover (B0) +1 fire barrier (B1 to B6)

7 chair types in triplicate tests: tot. of 21 chairs

All chair components protected by FB

9

Seams (Metal Staples) 

Dimensions in mm
Ignition Source

• Square Burner (18 kW for 80s) 

Flux Gauge

10
11

Effect of Fire Barriers: Videos

Fire barriers allows to:

• increase time to peak from 3 min (C0) to 22 min (C1 and C6)

• decrease PHRR from about 3 MW to about 1 MW

C0 C4 C1

Playback speed: 73x
What Happens Under the Chair?

12

Bottom Ignition (BI): persistent burning under the seat cushion due 

to the ignition of liquid product of pyrolysis
y = 1.0578x + 1.208

R2 = 0.9994

0

5

10

15

20

25

30

0 5 10 15 20 25

TTP 

- Time to PHRR (min)

TTBI - Time to Bottom Ignition (min)

Bottom Ignition (BI) and PHRR

Bottom Ignition leads to PHRR within (2 ± 1) min

13
Effect of Fire Barriers on HRR

Key Factors used to characterize the performance of the Fire Barrier:

TTBI and HRRBI

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35 40

HRR (kW)

Time (min)

Bottom Ignition (BI) with consequent pool-fire formation was always observed

TTBI

Time to BI 

Plateau Duration HRRBI

HRR at Bottom 

Ignition

14
Cube Test Set-up (Schematics) 

15

Insulation

4.25 in

FOAM

CUBE

Fire Barrier

Metal 

Frame

Fire Barrier

Cover Fabric

Catch pan

Cone heater:

75 kW/m2

TOP VIEW

BOTTOM 

VIEW

WIDE 

VIEW
Example of a Typical Cube Test

“Wetting”: appearance of visible liquid pyrolyzates on the bottom barrier 

Playback speed: 30x

Mass Transfer:

liquid pyrolyzates

16
Example of HRR Curve in Cube Test

17

0

1

2

3

4

5

6

0

200400600800

10001200

Time (s)

HRR (kW)

Wetting

HRR at Wetting

HRR

w

TTW

Time to Wetting
Cube to Full-Scale Correlation?

18

Correlation:

-TTBI to TTW?

-HRRBI to HRRw?
y = 0.1299x - 9.8593

R2 = 0.9872

0

5

10

15

20

25

50 100 150 200 250 300

TTW - Cube (s)

TTBI 

- Full Scale (min)

C3

Prediction of TTBI (and TTP) by Cube

ASTM D2261-13 (2017) 

Paper B1 B2 B3 B4 B5 B6

0

20

40

60

80

100

120

140 Tear Strength (N)

19
Prediction of Plateau Value 

y = 310.03x - 108.59

R2 = 0.9313

0

100

200

300

400

500

600

700

800

900

1000

0.0 0.5 1.0 1.5 2.0 2.5 3.0

HRRBI

- Full Scale (kW)

HRRW - Cube (kW)

20

C3
• In US, shifting from Chemical Fire Retardants toward Physical Mechanisms 

of Flame Retardancy (e.g., Fire Barriers)

• The Cube Test has been developed to capture Physical Mechanisms of 

Flame Retardancy (mass/heat transfer)

• Upholstered Furniture as a case study to prove the capability of the Cube 

Test to:

- predict Full-scale performance (within the limited data set available) 

- properly rank the effectiveness of Fire Barriers

21

Conclusions
22

THANK YOU!

Acknowledgements:

Contact Information:

Mauro Zammarano

Phone: 301-975-5244

e-mail: mauro.zammarano@nist.gov

Fire Research Division, NIST:

J. Randy Shields, Ickchan Kim, 

Isaac Leventon, Andre Thompson, 

Ronald Lankone, Anthony Hamins, 

Matt Bundy, Arthur Chernovsky
ASTM E05

-21 

WK65005

23

• Planning Interlaboratory Study

Products:

1. Insulation

2. Cored laminated composites

3. Upholstered furniture