The short answer is no. All businesses, no matter the size need to know what to do in a fire emergency situation and need someone as the “Go-To-Guy” for Health & Safety issues.
You might have fire extinguishers in the office or onsite, but does your staff know how to effectively use it? The equipment is only useful if people are trained to use it.
SHE Rep doesn’t have to be in house, but can be outsourced to a consultant. Each business needs to under have someone responsible for all the Health & Safety aspects.