Response Time Index (RTI) is a measure of thermal sensitivity of a sprinkler’s activation. It indicates how quickly the sprinkler responds to the heat from a fire. RTI is calculated by using the operating time, operating temperature, air temperature, air velocity, and conductivity factor of the sprinkler. RTI is independent of the gas velocity but depends on the properties of the sprinkler head such as mass, specific heat capacity andsurface area of the thermal sensing element. RTI is used to classify sprinklers into fast response or standard response categories.

References:The Basics of Sprinkler Thermal Characteristics | NFPA;Sprinkler Characteristics According to NFPA 13 - Fire Protection …;Response time index (RTI) - Oil and Gas Drilling Glossary;RESPONSE TIME INDEX OF SPRINKLERS - Department of Building Environment …

Spontaneous combustion is the exception to the requirement of a combustible material, an oxidizing agent, and an ignition source for combustion to take place. Spontaneous combustion is a phenomenon in which a material can ignite without any external heat or flame, due to a chemical reaction within the material that generates enough heat to reach the ignition temperature. Spontaneous combustion can occur in certain materials that are prone to self-heating, such as oily rags, hay, coal, and compost. Spontaneous combustion is a type of smoldering combustion, which is a slow, low-temperature, flameless form of combustion.References:

• Fire Protection Handbook, 20th Edition, Volume 1, Chapter 2, Section 2.2.1.11
• NFPA 921: Guide for Fire and Explosion Investigations, 2021 Edition, Section 4.3.12

The correct answer is A. Type I construction consists of structural members of approved noncombustible or limited combustible materials with specified fire resistance ratings for exterior bearing walls of 3 or 4 hours. This is the highest level of fire resistance among the five types of construction defined by NFPA 220: Standard for Types of Building Construction.Type I construction is typically used for high-rise buildings made of concrete and protected steel12

20 years.

According to NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, 2020 edition, fast response sprinklers are those that have a response time index (RTI) of 50 (m·s)^(1/2) or less.These sprinklers are designed to activate faster than standard response sprinklers in the event of a fire, and they are typically used in light hazard, ordinary hazard, and residential occupancies1

NFPA 25 requires initial testing of representative samples of fast response sprinklers after 20 years from the date of manufacture, and subsequent testing every 10 years thereafter. The testing involves removing a minimum of four sprinklers or 1% of the total number of sprinklers per individual sprinkler sample, whichever is greater, and sending them to a recognized testing laboratory. The laboratory will perform a plunge test, which measures the time it takes for the sprinkler to operate when exposed to a specified air temperature.The test results will indicate whether the sprinklers meet the acceptance criteria or need to be replaced123

References:

• NFPA 25: Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems1
• Sprinkler System Inspections, Testing, and Maintenance Frequencies Explained | NFPA4
• Sprinkler Testing on Quick Response Sprinklers: What You Need to Know2
• NFPA 25 ITM Quick Reference Guide - hillgrp.com3

OSHA regulation 1910.110 addresses storage and handling of liquefied petroleum gas (LPG). This regulation covers the general requirements for the design, construction, installation, operation, inspection, and maintenance of LPG systems, including containers, piping, valves, fittings, regulators, burners, and appliances. The regulation also specifies the safety precautions and procedures for the prevention of fire and explosion hazards involving LPG. The regulation applies to all employers who store, handle, or use LPG in their workplaces.References:

• OSHA: 1910.110 - Storage and handling of liquefied petroleum gases1
• Nebula Safety: Storage & Handling of Liquefied Petroleum Gases (LPGs)2

Fire alarm systems audible appliances ratings are usually stated as a sound pressure level (SPL) at 10 ft (3.05 m) from the appliance. The SPL is measured in decibels (dB) and indicates the loudness of the sound produced by the appliance. The SPL at 10 ft (3.05 m) is used as a standard reference point for comparing different audible appliances and for designing fire alarm systems to meet the required audibility levels.References:

• NFPA 72: National Fire Alarm and Signaling Code, 2019 Edition, Section 18.4.3.11
• Fire Protection Handbook, 20th Edition, Volume 1, Chapter 7, Section 7.8.2.12