# Zero Drop: ACS Gas Revision — Gas engineer CCN1 and CENWAT > Gas engineer CCN1 and CENWAT (iPhone/iPad app by AppyAppster Ltd.) - Source: https://appshunter.io/ios/app/zero-drop-acs-gas-revision/id6822322629 (this page in markdown: same URL + `.md`) - Developer: [AppyAppster Ltd](https://appshunter.io/developer/1746049419) - Category: Education, Reference - Price: Free - Age rating: 4+ - Requires: iOS 17.0 · 2 MB - Languages: British English - Released: 2026-10-28 - Data updated: 2026-11-01 ## What is Zero Drop? Revision for the ACS gas assessments: the theory papers UK gas engineers sit for the certificates that put them on the Gas Safe Register, and sit again every five years to stay on it. Zero Drop covers core domestic gas safety (CCN1) and boilers and water heaters (CENWAT). Independent and unofficial: Zero Drop does not represent any government entity. It is a study aid, not proof of competence, and is not affiliated with, endorsed by or connected to the Gas Safe Register, the Health and Safety Executive, IGEM, BSI or any ACS certification body or assessment centre. The assessments need every answer right, so accuracy comes first. Each question is written from the regulations and standards themselves and names the document and clause it rests on, so you can check it for yourself. Official sources Questions on the law are written from official, publicly available government texts: • Gas Safety (Installation and Use) Regulations 1998: https://www.legislation.gov.uk/uksi/1998/2451/contents • HSE L56, the Approved Code of Practice and guidance on those Regulations: https://www.hse.gov.uk/pubns/books/l56.htm • Gas Safety (Management) Regulations 1996: https://www.legislation.gov.uk/uksi/1996/825/contents • RIDDOR 2013: https://www.legislation.gov.uk/uksi/2013/1471/contents Questions on practice cite the British Standard or IGEM document and clause they rest on. No text from those documents is reproduced. Try it free Download free and try 15 questions from both modules, with every explanation and source in full. One in-app purchase unlocks every question, for good. No subscription, no account. What is in it 659 questions across 24 topics, from the Gas Safety (Installation and Use) Regulations and tightness testing to ventilation, flues, unsafe situations, condensate, controls and flue gas analysis. Each question has a level from 1 to 4, from foundations up to the tricky ones. How it works • Practise a module by topic and level, 10, 20 or 50 questions at a time, or all of them • Answer, and see straight away which option was right, with an explanation • See the document and clause to look it up in • On some questions, a note on why a tempting wrong answer is wrong, or a tip for the job • Flag any question to come back to • Go back over the questions you got wrong last time, or the ones you flagged • Review every session by all, correct, flagged or incorrect • See your progress per module, kept from one session to the next No adverts. No account. Your answers stay on your phone. There is no sign-in and nothing to set up. There are no adverts, no analytics and no crash reporting. Your answers, scores and flags are stored on your phone and never sent anywhere, and the questions work entirely offline. The one purchase is handled by the App Store. Zero Drop is made by AppyAppster Limited, a one-person studio in Glasgow. Support: support@appyappster.com Privacy: appyappster.com/privacy ## Is Zero Drop safe? Not enough ratings yet to assess Zero Drop. ## Is Zero Drop legit? Zero Drop: ACS Gas Revision appears legitimate, with a few gaps. The AppsHunter Legitimacy Score for Zero Drop is 75 out of 100 points across 7 verification signals from App Store and developer data. ## Version history (last 1 release) ### 1.0 — 2026-10-28 No release notes. ## More apps by AppyAppster Ltd - [TKD Quiz: TAGB Grading Theory](https://appshunter.io/ios/app/tkd-quiz-tagb-grading-theory/id550845370) - [TKD Guide: TAGB Syllabus](https://appshunter.io/ios/app/tkd-guide-tagb-syllabus/id972811189) - [Treadmill Smart Speed](https://appshunter.io/ios/app/treadmill-smart-speed/id1193076459) - [Treadmill Smart Speed V2](https://appshunter.io/ios/app/treadmill-smart-speed-v2/id6479820177) - [BlockRacer](https://appshunter.io/ios/app/blockracer/id6755129055) All apps by AppyAppster Ltd: https://appshunter.io/developer/1746049419 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-11-01.*