BS 7175 Source 7: Flammability test for bedding in UK prisons and high-risk settings.

In most commercial fire safety contexts, standards are designed to prevent “accidents.” However, in prisons, custody suites, and secure mental health units, fire safety must address a much darker threat: “Arson.” This guide analyzes BS 7175 Source 7—the UK’s most rigorous fire testing standard for bedding in high-risk environments—and clarifies the critical differences between BS 7177 and BS 5815.

1. What is the BS 7175 Standard?

BS 7175 (Full title: Methods of test for the ignitability of bedcovers and pillows by smouldering and flaming ignition sources) is the specific UK test method standard used to assess the flammability of bed covers, pillows, and duvets. It utilizes ignition sources ranging from 0 to 7 to simulate fire risks varying from a smouldering cigarette to deliberate arson.

Within this standard, Source 7 (Crib 7) represents the highest level of testing intensity, specifically designated for environments classified as “Very High Hazard.”

2. Why is Source 7 Needed? Understanding “Very High Hazard”

Source 7 exists to counter the risk of deliberate ignition in confined environments. In ordinary hospitals or hotels (typically Source 5), fire risks usually stem from accidental matches or cigarettes. However, in the following institutions, occupants may display aggressive or self-harming behavior and may attempt to create severe fires by piling up clothing or newspapers on a bed:

• HM Prisons (HMP) & Ministry of Justice (MoJ) facilities
• Police Custody Suites
• Secure Mental Health Units
• Offshore Oil Rig Accommodation

In these environments, standard fire retardancy is insufficient to prevent “Flashover.” Only products that pass Source 7 can ensure that, even in cases of arson, the fire remains contained within a minimal area.

3. The BS 7175 Ignition Source Hierarchy

BS 7175 uses an exponential numbering system (0-7) to classify risk. Understanding the energy difference between these sources is crucial for selecting the correct product.

Ignition Source	Type	Energy Description	Typical Application
Source 0	Lit Cigarette	Smouldering, no open flame.	Domestic, Low Risk.
Source 5 (Crib 5)	Wood Crib (~17g)	Medium intensity open flame.	NHS Wards, Hotels.
Source 7 (Crib 7)	Large Wood Crib (~35g)	Extreme intensity (2x energy of Source 5).	Prisons, Custody, Secure Units.

4. The BS 7175 Source 7 Test Procedure

The Source 7 test is a highly destructive process designed to verify structural integrity under extreme heat radiation.

4.1 Sample Assembly (Composite Test)

Testing must be conducted as a “Composite.” The actual pillowcase/duvet cover must be tested in combination with the specific inner filling (pillow core/duvet insert) intended for use. This ensures the test reflects the performance of the finished product.

4.2 Application of Ignition

Testers construct a large lattice crib made of specific pine wood (Crib 7) and add Isopropyl alcohol as an accelerant. Once ignited, this crib generates ferocious flames and sustained high-temperature radiant heat.

4.3 Pass/Fail Criteria

To pass, the sample must meet the following within 60 minutes: No Penetration (flame must not burn through to the underside), Self-Extinguishing (fabric flames must die out after the wood is consumed), and No Flaming Debris.

5. Core Comparison: BS 7177 vs. BS 7175 vs. BS 5815

These three standards are frequently confused in procurement. To ensure compliance, it is vital to distinguish their test objects and applicable scenarios.

5.1 The Golden Rule of Definitions

• BS 7177 → For Mattresses: The performance specification for finished mattresses (covering all levels from domestic Low Hazard to prison Very High Hazard).
• BS 7175 → For Bedding: The test method for pillows, duvets, and bedspreads (specifically referring to Source 7 in prison contexts).
• BS 5815 → For Hospital Sheets: A specification for lightweight NHS bedding focusing on washability.

5.2 Detailed Comparison Table

Feature	BS 7177 (Mattress Spec)	BS 7175 (Bedding Test)	BS 5815 (Hospital Spec)
Test Object	Mattresses Divan Bases	Pillows Duvets (Quilts) Bedspreads	Sheets Duvet Covers Blankets
Max Source	Source 7 (Crib 7) *(For Very High Hazard)*	Source 7 (Crib 7) *(For Prison/High Risk)*	Source 5 (Typically) *(Weaker source, focus on wash)*
Key Feature	Fire resistance of the finished unit.	Anti-vandal & Arson resistance.	Durability over 50+ thermal washes.
Primary Scenario	All Locations (Graded by risk).	Primarily Prisons & Custody.	Primarily NHS Hospitals.

5.3 Clarifying Industry Myths

Myth: “BS 7177 does not go up to Source 7; it is less strict than BS 7175.”
Fact: This is a critical error. The “Very High Hazard” classification within BS 7177 explicitly mandates testing with Source 7. In a prison cell, the mattress must comply with BS 7177 (Source 7), and the bedding must comply with BS 7175 (Source 7). They are a matching system, not substitutes.

6. Technical Insights: How to Pass Source 7?

To withstand “Hellfire,” BS 7175 Source 7 products typically rely on the following engineering:

1. High-Performance Fibers: Utilizing Modacrylic or Aramid (Kevlar-type materials). These carbonize to form a hard “Char” shield rather than melting.
2. High-Density Structure: Fabric weight is typically >250gsm. Often includes specialized coatings to be not only fire-resistant but also Anti-ligature (tear-resistant) to prevent suicide attempts.
3. Fully FR Composition: Internal fillings must be FR Hollow Fiber. If standard polyester is used inside, heat penetrating the fabric will ignite the core, causing the pillow to explode from the inside out.

7. FAQ: Frequently Asked Questions