Materials and construction EN 812 Clause 4.1 Cofia EN 812 Clause 4.2 Sweatband EN 812 Clause 4.3 Retention EN 812 Clause 4.4 headband/nape strap EN 812 Clause 4.5 Chin strap EN 812 Clause 4.6 Ventilation EN 812 Clause 4.7 Accessories EN 812 Clause 4.8 Pre-conditioning low Tª EN 812 Clause 6.2.2 Pre-conditioning high Tª EN 812 Clause 6.2.3 Pre-conditioning water immersion EN 812 Clause 6.2.4 Pre-conditioning artificial ageing EN 812 Clause 6.2.5 Impact absorption EN 812 Clause 6.5 Resistance to penetration EN 812 Clause 6.6