Posted By ian milne No but consider the following 'elements': weight of unit, comfortability, entanglement issues (often due to sticking out hoses), ease of fitment/donning/doffing, breathing resistance, frequency of filter change, availability of spares and how did you feel at the end of the week (a day is to short and they would need to get used to the additional weight so fitness develops). The employee needs to made to understand that he will wear something (wether its this model or another) and he will need to adjust is manoeuvrability and posture but it will benefit him medium term. Also, beware that suppliers will try and sell you anything however practical or not their equipment is. Trust this assists. Ian Milne