# Public Address & Voice Alarm (PAVA) Systems ## Overview Public Address & Voice Alarm (PAVA) systems are specialised sound systems designed to deliver **life safety messages** during an emergency, in addition to providing public address and background audio functions during normal operation. In the UK, PAVA systems are treated as **safety services** under the **Electricity at Work Regulations 1989 (EAWR)** and must be installed, operated, and maintained in accordance with electrical safety legislation and relevant British/European standards. --- ## Regulatory Framework ### Electricity at Work Regulations 1989 (EAWR) * All electrical systems must be constructed and maintained so as to **prevent danger**. * Applies to **PAVA systems** because: * **100 V line speaker circuits** exceed the 50 V AC extra-low voltage (ELV) threshold → classed as **Low Voltage (LV, Band II)**. * Amplifier and PSU components often run at **300-600 V internally**, requiring competent persons for installation and servicing. * **Implication:** Only those with **appropriate electrical training and competence** should install or modify PAVA cabling and equipment. --- ## Standards and Compliance ### Design & Installation * **BS 5839-8** - Code of practice for voice alarm systems. * **BS EN 54-16** - Voice alarm control and indicating equipment. * **BS EN 54-24** - Loudspeakers for voice alarm. * **BS EN 54-4** - Power supply equipment. * **BS 7671 (IET Wiring Regs)** - Electrical safety, including: * Section 560: Safety services. * Section 534: Surge protection (with reference to **BS EN 62305** lightning protection). ### Cabling & Fire Resistance * **BS 8434-1 & -2** - Fire test methods for cable survival. * **BS 8519** - Selection/installation of fire-resistant cable systems for life safety and firefighting systems. * **Enhanced fire-resisting cables** generally required in stadiums, hospitals, tunnels, transport hubs. ### Operational Requirements * PAVA must always have **priority** over background music, advertising, or commentary. * Messages must be **intelligible** (tested via STIPA/STI). * Systems must provide **24 h standby + 30 min full alarm operation** on battery supply. --- ## Electrical Safety Considerations ### 100 V Line Circuits * Operate at **70-100 V RMS AC audio signal** → **Band II (LV)** under **BS 7671**. * Requires electrical competence for installation and testing (continuity, insulation resistance, polarity). * Must be segregated from Band I circuits (fire alarm loops, ELV data/control). ### High-Voltage Internal Components * Amplifiers, PSU units, and changeover modules can operate with **300-600 V DC rails** internally. * Only competent persons should access live enclosures. * Risk assessments under EAWR required before live testing/maintenance. ### Surge & Lightning Protection * Long 100 V lines between buildings or across stadium/transport sites are susceptible to induced surges. * Must be protected via SPDs as per **BS 7671:534** and **BS EN 62305-4**. * Fibre-optic distribution (immune to surges) is increasingly preferred for backbone links. --- ## Health & Safety Competence * Because **100 V PAVA lines are Low Voltage**, staff without formal electrical training (e.g. general fire/security engineers) should not install or modify them. * Competency requirements: * **Electricians** or those with equivalent LV training: Installation & testing. * **PAVA specialists/commissioning engineers**: Programming, zoning, intelligibility testing. * **Joint training** recommended for multidisciplinary teams. --- ## Related Standards & Guidance * **BS 9999 / BS 9991** - Fire safety design and evacuation strategy (defines when VA is required). * **BS 8644-1** - Digital records (golden thread) → commissioning/test results must be recorded. * **EAWR 1989** - Legal obligation to ensure safe electrical systems at work. --- ## Electrical Safety & Competence (EAWR Context) PAVA systems, particularly those built on **100 V line distribution**, operate with internal voltages of **up to 600 V**. Both the line outputs and the amplifier internals far exceed the 50 V AC “safe touch” threshold defined in UK legislation. ### The EAWR Position The **Electricity at Work Regulations 1989 (EAWR)** require that: * No person shall be engaged in work on or near electrical equipment unless they have the **knowledge, training, and experience** to do so safely (Regulation 16). * The employer must ensure **safe systems of work** are in place, including isolation, lock-off, test-before-touch, and risk assessment. ### Competence Boundaries in Practice * **Fire Alarm Engineers** * Competence is usually centred on **ELV/SELV systems** (≤ 50 V AC / 120 V DC). * Many are not electrically qualified to work on **LV mains supplies** (e.g., 230 V panel feeds) or **100 V line terminations**. * In strict compliance terms, their role is limited to: * Programming, configuration, and software-based commissioning. * Functional testing once the electrical installation has been safely completed and energised by a competent person. * Visual inspection of wiring for correct segregation and containment. * **Electrically Competent Persons (Electricians / Electronics Engineers)** * Required for: * Terminating and testing 100 V line speaker circuits. * Installing and energising panel mains supplies. * Working inside amplifiers with HV rails (400-600 V). * Carrying out repairs, replacements, and component-level fault-finding. ### Practical Implications * Fire alarm companies often rely on **electricians to install and terminate PAVA cabling** (both mains and 100 V lines). * Fire alarm engineers then **commission the system in software and functionally test it**, but do not carry out electrical works. * This split of responsibility ensures compliance with EAWR while still allowing specialist fire engineers to handle system logic, cause-and-effect, and voice message testing. --- **Key Point**: Under EAWR, **fire alarm engineers are not automatically qualified to work on 100 V line circuits or panel mains feeds**. Their role is restricted to the *non-electrical aspects* of commissioning and maintenance, with all electrical terminations and HV work carried out by appropriately trained and authorised electrical personnel. --- ## Summary PAVA systems in the UK are not just audio equipment - they are **life safety electrical installations**. * **100 V line circuits = Low Voltage (Band II)** under BS 7671 → must be treated as such for segregation and safety. * Internal components may operate at **up to 600 V**, meaning EAWR competence rules apply. * Compliance requires integration of **fire safety standards (BS 5839-8, EN 54)** with **electrical regulations (BS 7671, BS 8434, BS 8519, EAWR 1989)**. * Only competent, trained personnel should design, install, or maintain PAVA systems.