Travel Direct vs Direct Distance and Ways to limit spread of fire Q6

Q.
(a) Explain the difference between travel distance and direct distance as means of escape in case of fire. (15 marks)

(b) Explain two (2) ways of limiting the spread of fire in a high rise building. (10 marks)

(25 marks, 2016 Q6)

A.
a) Travel distance vs direct distance (Common Path of Egress Travel go here)

"Travel Distance Means of escape" - Primary principle of means of escape

Alternative means of escape made possible
Is the direct shortest route to a place of safety – outside of building

If in building – a protected or isolated passage way stairs or refuge which lead to outside of building.

Generally 'means of escape' consists of two parts

Unprotected areas leading direct to exit
Protected areas leading direct to exit exam

Unprotected areas forming escape routes are to be limited in distance to minimize exposure to smoke and fire and this is the basis of "Travel Distance".

Travel distance is described in Section 1016.1 (2009 IBC) as the maximum length of exit access travel, measured from the most remote point within a story along the natural and unobstructed path of egress travel to an exterior exit door at the level of exit discharge, an entrance to a vertical exit enclosure, an exit passageway, a horizontal exit, an exterior exit stairway or an exterior exit ramp, [which] shall not exceed the distances given in Table 1016.1.

In essence, it is the total distance an occupant must cover to reach an exit as defined by the IBC (See Figure 1). The concern with travel distance is to ensure that occupants can reach an exterior door or protected exit enclosure without having to take an extremely long path to get there, thus reducing the occupants’ exposure to a potential hazard.

Table 1016.1 provides the limitations on travel distance based on occupancy and the installation of a sprinkler system. For most nonsprinklered occupancy groups, this distance is 200 feet.

With a sprinkler system installed, this distance increases to 250 feet, but for B occupancies, it increases to 300 feet.

Nonsprinklered Groups F-2, S- 2, and U are limited to 300 feet (400 feet when sprinklered). Group I and H occupancies have various travel distances listed, but are limited to only sprinklered buildings, since these occupancies are required to be sprinklered per Section 903.2.

Ref:
http://www.specsandcodes.com/articles/code_corner/The%20Code%20Corner%20No.%2029%20-%20Travel%20Distance.pdf

Direct Distance

Direct distance is the straight line to the exit point.

It is not a 'realistic distance' but is a imaginary distance.

Usually, it should be not less than 2/3 of the travel distance. Which means if there are lots of objects blocking the path, the direct distance/travel distance would be lesser than 2/3.

Ref:
Chapter 2: Means of escape. Fire Safety, available at,
https://www.scdf.gov.sg/content/scdf_internet/en/building-professionals/publications_and_circulars/fire_code_2002handbooks/_jcr_content/par/download_4/file.res/hb_v3_ch2.pdf

b) 2 ways of limiting the spread of fire in a high rise building

1. Fire Door - to limit the fire inside the room from spreading.

2. Smoke detector - sprinkle system to extinguish the fire within the room as soon as possible, and making it difficult to spread.

The overall strategy to fire risk control in a high rise building can be shown in the diagram below:

Ref:
Ken Richardson. Fire safety in high rise apartment buildings. Ontaria Association of Architects. Available online at,
https://www.slideshare.net/mobile/FeritFazliu1/fire-safetyinhighriseapartmentbuildings