How many men are needed to break Yichud at night?
In general, for Ashkenazim, it suffices to have two Kosher men to break Yichud. This however only applies during the daytime and while in the city, however at nighttime or during travel outside of the city, three Kosher men are required. [This, however, applies only from the time of night that people generally go to sleep. However, at night, prior to the time that people usually go to sleep, it has the same status as daytime, and only two Kosher men are required. The three men are valid even if some or all are currently sleeping.]
Men who are Perutzim: It is forbidden for a woman to be alone with men who are Perutzim, even if there are ten or more, unless another Yichud breaker is applicable. A typical religious Jew is considered to be Kosher, [unless there is reason to suspect otherwise].
In order to break Yichud at night, starting from the time that people usually go to sleep, three kosher men are required.
Ø Inviting men to one’s home: It is permitted for a woman to allow two Kosher men to enter her home during the daytime, even if no other Yichud breaker is applicable [i.e. door is closed, no husband in city]. Furthermore, even at nighttime, if they’re coming for a short visitation and then leaving it is permitted for two men to visit even late at night. However, if they’re coming to stay for the night then three men are required, as stated above.
Ø Traveling with men: A woman may travel in the same car with three Kosher men present, even if it is late at night and they’re traveling outside the city.
Ø Working in office with men: It is permitted for a woman to work in an office alone with two Kosher men, so long as they do not remain late pass the time that people usually go to sleep, in which case three kosher men are required.
Until what time is it considered night with regards to requiring three kosher men?
Ø Can a woman get a ride to the airport at 5:00 AM if they will be traveling through areas in which people and cars are scarce at that hour, and there will be two Kosher men in the car?
It is defined as nighttime to require three Kosher men until the time of morning that people normally wake up, even if it’s already past daybreak. Accordingly, in the above example, three Kosher men are to travel in the car if they will be passing through unpopulated areas. [Indeed, if they are traveling through unpopulated areas outside of the city, then this would be required regardless even during daytime, due to the fact that they are traveling.]
 See Michaber and Rama E.H. 22:5; Tur 22:5; Devar Halacha 9:17; Nitei Gavriel 20:1-2
 Rama ibid; Tur 22:5 in name of Rosh; Tana Kama in Kiddushin 80b
Other opinions: Some Poskim rule that a woman may not be alone even with many men unless another Yichud breaker is applicable. [Michaber 22:5; Tur 22:5 in name of Rambam Issurei Biyah 22:8; Rebbe Shimon in Kiddushin ibid] The Sephardi custom is like this opinion. [Heard from Harav Yaakov Yosef; Nitei Gavriel 17:2]
 Rama ibid; Beis Yosef in name of Raavad Baalei Nefesh Shaar Haperisha p. 95; Chochmas Adam 126:5; Kitzur SHU”A 152:3; Chazon Ish;
 Chasam Sofer E.H. 2:96; Devar Halacha 9:17; Nitei Gavriel 20:2
 Ravad in Baal Hanefesh Shaar Haperisha; Devar Halacha ibid; Nitei Gavriel ibid footnote 2
 Rama ibid; See Nitei Gavriel 19
 Devar Halacha ibid; Nitei Gavriel ibid footnote 5
 Vetzaruch Iyun if three Kosher men should always be required in such a case, due to Libo Gas Bah, and Isko Im Nashim. See Nitei Gavriel 19:7-8
 Nitei Gavriel 20:5