2. Can the security staff of a building ask me to enter my ID card number in a visitors' log book at the entrance of a building?
This depends on whether the monitoring of your activities inside the building is feasible or not (e.g. is it feasible to arrange a security guard to accompany you inside the building). If this is feasible, the security staff should not collect your ID card number. If such monitoring is not feasible, they are allowed to collect your ID card number.
However, the security staff should take appropriate security measures to ensure that such entries in a visitors' log book are concealed from subsequent visitors who enter their details. If you are unwilling to provide your ID card number, you can suggest other alternatives. Examples of such alternatives include identification by another identification document (e.g. a staff card), or identification by someone known to the security staff (e.g. by a resident in the case of a residential building).
It is recommended by the Privacy Commissioner's Office that in normal circumstances, entries in the visitor log book can be retained for a period of not more than one month. If there are any valid grounds justifying a longer retention period (e.g. where the records are required for evidentiary purposes or to assist a police investigation of detected or reported unlawful activities), the security staff can retain the data for more than one month. For more guidelines on this matter, please refer to the PCO's publication "Personal Data Privacy: Guidance on Property Management Practices".