My take is maybe stanard response were installed to begin with and quick reponse have replaced some of them. Now why they were replaced is a good question, unless there was a fire, recall, or leak or similar.
But anyway to your question::
from 2010
8.3.3 Thermal Sensitivity.
8.3.3.1*
Sprinklers in light hazard occupancies shall be one of the following:
(1)
Quick-response type as defined in 3.6.4.7
(2)
Residential sprinklers in accordance with the requirements of 8.4.5
(3)
Standard-response sprinklers used for modifications or additions to existing light hazard systems equipped with standard-response sprinklers
(4)
Standard-response sprinklers used where individual standard-response sprinklers are replaced in existing light hazard systems
A.8.3.3.1
A.8.3.3.1 When renovations occur in an existing building and no changes are made in the existing sprinkler system, this section is not intended to require the replacement of existing standard sprinklers with quick-response sprinklers.
and from 2010 commentary:::
The use of quick-response sprinklers, which are specified in 8.3.3.1(1), has been an option within NFPA 13 since the 1980 edition. Although quick-response sprinklers tend to enhance property protection and life safety, no requirements or incentives for their use were provided until the 1996 edition. The requirement that quick-response sprinklers be used in all light hazard occupancies, with appropriate exceptions to address existing systems, raises the baseline level of system performance.
"""""""""""""""Existing systems are not required to be upgraded when renovations occur.""""""""""""""
Quick-response sprinklers are considered necessary because of their life safety benefits. The evidence clearly indicates that using quick-response sprinklers rather than standard-response sprinklers reduces the fire damage, all other factors being equal. Most of the sprinkler systems installed in light hazard occupancies, such as hospitals, hotels, and apartments, are installed for life safety purposes. However, even in those occupancies where life safety is not the primary reason for sprinkler system installation, such as in offices and restaurants, quick-response sprinklers are still considered important, because they limit fire damage and the potential for injury or death of occupants and fire fighters. Given the current level of knowledge concerning the performance of quick-response sprinklers, the use of standard-response technology instead of quick-response technology in light hazard occupancies is considered inappropriate.
Like quick-response sprinklers, residential sprinklers have fast-response operating elements and can be used within some light hazard occupancies in accordance with 8.4.5. However, residential sprinklers and quick-response sprinklers have different spray patterns. Therefore, residential sprinklers should be used only as outlined in 8.4.5, and quick-response spray sprinklers should be used in other portions of the light hazard occupancies.
In some occupancies that are traditionally considered light hazard, ordinary hazard designs are sometimes used due to an uncertainty in the fire loading. Office buildings are an example of this type of occupancy. In these cases, quick-response sprinklers should be used, even though a higher sprinkler density is provided by using an ordinary hazard design.
as long as they are the same temp heads and K factor should be ok, unless there is something else going on????????