Which sprinkler type is secured with an extension nipple and seal?

The correct choice highlights the unique installation characteristics of a dry sprinkler. Dry sprinklers are designed specifically for areas that may be exposed to freezing temperatures. They feature a mechanism that prevents water from entering the sprinkler until it is activated by heat, allowing the sprinkler to be installed in locations where a traditional wet system could fail.

An extension nipple and seal are vital for making sure that the dry sprinkler remains airtight and properly sealed at the connection point. This prevents any water from leaking out of the system and maintains the effectiveness of the sprinkler's operation in emergency situations. The extension nipple helps in accommodating the sprinklers' placement further away from the pipe, ensuring that the installed design functions correctly without risking freezing water from clogging or leaking at the connection point.

Other sprinkler types do not require this specific sealing mechanism due to their design and intended environments. For instance, sidewall sprinklers and upright sprinklers function in conditions where water is always present, eliminating concerns related to freezing or improper sealing. Corrosion-resistant sprinklers are used in environments susceptible to corrosion but don’t inherently require the same type of extension fixtures for operation.