(e) ACGIH ® Threshold Limit Values (TLV ® s) (ACGIH ® 2017). TLV ® s are listed in the order of 8-hour time weighted averages (TWAs), STELs (ST), and Ceilings (C), if available. ACGIH ® has established TLVs ® for compounds not included in the OSHA Z Tables. Please see ACGIH ® Documentation for additional limits, skin absorption and other designations, and explanations. The 2017 TLV ® and BEI ® Book and Documentation of the Threshold Limit Values on Chemical Substances, 7th Edition are available through the ACGIH ® website at http:// . The TLVs ® and BEIs ® are copyrighted by ACGIH ® and are not publicly available. Permission must be requested from ACGIH ® to reproduce the TLVs ® and BEIs ® . Click here for permission request form.
If the source is reporting on empirical data, describe the research methods and summarise the results. Give an overview of the general design of the study, . survey, interview; the participants and any limitations of the study, . sample size or geographic area. "This article presents findings from a study into the use of social network sites for educational purposes. Surveys were conducted with 300 students to evaluate whether this medium is an appropriate way to disseminate unit assessment requirements and support information. The participants in the sample were aged between 18 and 50, included 120 males and130 females and were a mixture of domestic and international students"